{"id":2521,"date":"2026-05-28T17:13:15","date_gmt":"2026-05-28T11:43:15","guid":{"rendered":"https:\/\/mymockmate.com\/notes\/?p=2521"},"modified":"2026-07-24T13:23:01","modified_gmt":"2026-07-24T07:53:01","slug":"ncert-class-9-science-atomic-foundations-of-matter-solutions","status":"publish","type":"post","link":"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-atomic-foundations-of-matter-solutions\/","title":{"rendered":"NCERT Class 9 Science Chapter 9 Atomic Foundations of Matter  Solutions"},"content":{"rendered":"<div class=\"mymoc-top mymoc-entity-placement\" id=\"mymoc-3599263582\"><div id=\"mymoc-2336915049\"><a href=\"https:\/\/amzn.to\/4ehJfM4\" aria-label=\"students acessories\"><img src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories.png\" alt=\"\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories.png 1301w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories-300x85.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories-1024x290.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/students-acessories-768x218.png 768w\" sizes=\"(max-width: 1301px) 100vw, 1301px\" width=\"1080\" height=\"100\"><\/a><\/div><\/div>\n<h1 class=\"wp-block-heading\">Short Intro<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">This chapter introduces the atomic nature of matter and explains how atoms combine to form molecules and compounds. Students learn important laws of chemistry, chemical bonding, writing chemical formulae, ionic and covalent compounds, and molecular mass through solved examples and numerical problems.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Quick Information Box<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Topic<\/th><th>Details<\/th><\/tr><\/thead><tbody><tr><td>Chapter<\/td><td>Atomic Foundations of Matter<\/td><\/tr><tr><td>Class<\/td><td>Grade 9<\/td><\/tr><tr><td>Subject<\/td><td>Science<\/td><\/tr><tr><td>Main Topics<\/td><td>Chemical Bonding, Atoms, Molecules<\/td><\/tr><tr><td>Important Laws<\/td><td>Conservation of Mass, Constant Proportions<\/td><\/tr><tr><td>Key Bond Types<\/td><td>Ionic Bond and Covalent Bond<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h1 class=\"wp-block-heading\">Concepts Used (Topics Covered)<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Law of Conservation of Mass<\/li>\n\n\n\n<li>Law of Constant Proportions<\/li>\n\n\n\n<li>Dalton&rsquo;s Atomic Theory<\/li>\n\n\n\n<li>Molecules and Chemical Bonds<\/li>\n\n\n\n<li>Covalent Bond Formation<\/li>\n\n\n\n<li>Ionic Bond Formation<\/li>\n\n\n\n<li>Cations and Anions<\/li>\n\n\n\n<li>Writing Chemical Formulae<\/li>\n\n\n\n<li>Properties of Ionic and Covalent Compounds<\/li>\n\n\n\n<li>Molecular Mass<\/li>\n\n\n\n<li>Formula Unit Mass<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Important Formulas<\/h1>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Mass of Reactants = Mass of Products<\/li>\n\n\n\n<li>Number of Neutrons<br>= Mass Number &minus; Atomic Number<\/li>\n\n\n\n<li>Molecular Mass<br>= Sum of Atomic Masses of All Atoms<\/li>\n\n\n\n<li>Formula Unit Mass<br>= Sum of Atomic Masses in Ionic Compound<\/li>\n\n\n\n<li>Chemical Formula by Criss-cross Method<\/li>\n<\/ol>\n\n\n\n<h1 class=\"wp-block-heading\">Questions &amp; Step-by-step Solutions with Explanation<\/h1>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<p class=\"has-luminous-vivid-orange-color has-text-color has-link-color has-x-large-font-size wp-elements-1 wp-block-paragraph\"><strong>Think It Over<\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>1. Water can be obtained from various sources. Are all these samples of water chemically identical?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img fetchpriority=\"high\" decoding=\"async\" width=\"859\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-380-859x1024.png\" alt=\"\" class=\"wp-image-4250\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-380-859x1024.png 859w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-380-252x300.png 252w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-380-768x915.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-380.png 1149w\" sizes=\"(max-width: 859px) 100vw, 859px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">2. <strong>Oxygen is sometimes represented as O and sometimes as O<sub>2<\/sub> . What is the difference  between these symbols?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"952\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-381-952x1024.png\" alt=\"\" class=\"wp-image-4251\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-381-952x1024.png 952w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-381-279x300.png 279w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-381-768x826.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-381.png 1209w\" sizes=\"(max-width: 952px) 100vw, 952px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">3. <strong>Why does dissolved salt in water conduct electricity, but sugar does not?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img decoding=\"async\" width=\"899\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-382-899x1024.png\" alt=\"\" class=\"wp-image-4252\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-382-899x1024.png 899w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-382-263x300.png 263w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-382-768x875.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-382.png 1175w\" sizes=\"(max-width: 899px) 100vw, 899px\"><\/figure>\n\n\n\n<p class=\"has-luminous-vivid-orange-color has-text-color has-link-color has-x-large-font-size wp-elements-2 wp-block-paragraph\"><strong>Pause and Ponder<\/strong><\/p>\n\n\n\n<div class=\"internal-linking-related-contents\"><a href=\"https:\/\/mymockmate.com\/notes\/class-9-maths-exercise-1-1-solutions-coordinate-geometry-ncert-solutions\/\" class=\"template-2\"><span class=\"cta\">Related Topic to Read more<\/span><span class=\"postTitle\">NCERT Class 9 Maths Exercise 1.1 Solutions | Coordinate Geometry NCERT Solutions<\/span><\/a><\/div><p class=\"has-medium-font-size wp-block-paragraph\">1. <strong>A student burns 10 g of ethanol in an open beaker. After the reaction, no residue is left in the beaker. Does this mean the Law of Conservation of Mass is violated? Explain.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"859\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-383-859x1024.png\" alt=\"\" class=\"wp-image-4255\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-383-859x1024.png 859w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-383-252x300.png 252w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-383-768x915.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-383.png 1149w\" sizes=\"(max-width: 859px) 100vw, 859px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\">2. <strong>When 20 g of hydrogen reacts completely with 160 g of oxygen, how much water is formed<br>according to the Law of Conservation of Mass?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"934\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-384-934x1024.png\" alt=\"\" class=\"wp-image-4256\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-384-934x1024.png 934w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-384-274x300.png 274w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-384-768x842.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-384.png 1198w\" sizes=\"(max-width: 934px) 100vw, 934px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>3. A compound consists of 40% sulfur and 60% oxygen by mass. In a sample of the same compound containing 20 g of sulfur, what mass of oxygen must be present to satisfy the Law<br>of Constant Proportions?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-386-1024x683.png\" alt=\"\" class=\"wp-image-4258\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-386-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-386-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-386-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-386.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>4. Carbon monoxide (CO) contains carbon and oxygen in the mass ratio of 3:4. How much<br>oxygen will combine with 9 g of carbon to form carbon monoxide?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-385-1024x819.png\" alt=\"\" class=\"wp-image-4257\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-385-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-385-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-385-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-385.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>5. The Law of Definite Proportions holds true for compounds but not for mixtures. Give reason.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"901\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-387-901x1024.png\" alt=\"\" class=\"wp-image-4261\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-387-901x1024.png 901w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-387-264x300.png 264w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-387-768x873.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-387.png 1176w\" sizes=\"(max-width: 901px) 100vw, 901px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>6. Students X and Y, both prepared an oxide of copper by combining copper and oxygen in the<br>ratios of 4:1 and 8:2, respectively. Do their results justify the Law of Constant Proportions?<br>Explain.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"934\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-388-934x1024.png\" alt=\"\" class=\"wp-image-4262\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-388-934x1024.png 934w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-388-274x300.png 274w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-388-768x842.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-388.png 1198w\" sizes=\"(max-width: 934px) 100vw, 934px\"><\/figure>\n\n\n\n<div class=\"internal-linking-related-contents\"><a href=\"https:\/\/mymockmate.com\/notes\/class-9-maths-exercise-1-2-solutions-coordinate-geometry-ncert-solutions\/\" class=\"template-2\"><span class=\"cta\">Related Topic to Read more<\/span><span class=\"postTitle\">NCERT Class 9 Maths Exercise 1.2 Solutions | Coordinate Geometry NCERT Solutions<\/span><\/a><\/div><p class=\"has-medium-font-size wp-block-paragraph\"><strong>7. Assertion (A): 2 g of hydrogen combines with 16 g of oxygen to form 18 g of water.<br>Reason (R): According to Dalton&rsquo;s Atomic Theory, atoms combine in a simple whole number<br>ratio by mass to form compounds.<br>Choose the correct option:<br>(i) Both A and R are true, and R is the correct explanation of A.<br>(ii) Both A and R are true, but R is not the correct explanation of A.<br>(iii) A is true, but R is false.<br>(iv) A is false, but R is true.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"864\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-389-864x1024.png\" alt=\"\" class=\"wp-image-4263\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-389-864x1024.png 864w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-389-253x300.png 253w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-389-768x910.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-389.png 1152w\" sizes=\"(max-width: 864px) 100vw, 864px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>8. Nitrogen has five valence electrons. Draw the structure of the nitrogen molecule (N<sub>2<\/sub>).<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-390-1024x819.png\" alt=\"\" class=\"wp-image-4266\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-390-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-390-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-390-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-390.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>9. The atomic number of fluorine is 9. Explain the formation of the fluorine molecule (F2).<\/strong><\/p><div class=\"mymoc-middle mymoc-entity-placement\" id=\"mymoc-482215759\"><div id=\"mymoc-2225207000\"><a href=\"https:\/\/amzn.to\/4upqwUD\" aria-label=\"laptop-1\"><img src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/laptop-1.png\" alt=\"\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/laptop-1.png 1303w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/laptop-1-300x91.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/laptop-1-1024x310.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/laptop-1-768x233.png 768w\" sizes=\"(max-width: 1303px) 100vw, 1303px\" width=\"1303\" height=\"395\"><\/a><\/div><\/div>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-391-1024x819.png\" alt=\"\" class=\"wp-image-4267\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-391-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-391-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-391-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-391.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>10. Show the formation of the following molecules:<\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>(i) Carbon dioxide (CO<sub>2<\/sub>)<br>(ii) Hydrogen sulfide (H<sub>2<\/sub>S)<br>(iii) Ammonia (NH<sub>3<\/sub>)<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"859\" height=\"1024\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-392-859x1024.png\" alt=\"\" class=\"wp-image-4268\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-392-859x1024.png 859w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-392-252x300.png 252w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-392-768x915.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-392.png 1149w\" sizes=\"(max-width: 859px) 100vw, 859px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>11. Neon (atomic number 10) neither transfers nor shares its valence electrons. Explain.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-393-1024x819.png\" alt=\"\" class=\"wp-image-4269\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-393-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-393-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-393-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-393.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<div class=\"internal-linking-related-contents\"><a href=\"https:\/\/mymockmate.com\/notes\/class-9-maths-end-of-chapter-exercise-solutions-coordinate-geometry-ncert-solutions\/\" class=\"template-2\"><span class=\"cta\">Related Topic to Read more<\/span><span class=\"postTitle\">NCERT Class 9 Maths End of Chapter Exercise Solutions | Coordinate Geometry<\/span><\/a><\/div><p class=\"has-medium-font-size wp-block-paragraph\"><strong>12. What kind of ion will oxygen (O) form?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-394-1024x819.png\" alt=\"\" class=\"wp-image-4270\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-394-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-394-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-394-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-394.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>13. Fill in the blanks.<br>Among magnesium and chlorine, magnesium atom can give two electrons to become Mg<sup>2+<\/sup>. However, chlorine can take only one electron to become ______<em><em>_<\/em>. Now, <em>_<\/em><\/em>_____ ion of magnesium and <em>__<\/em>_____ ions of chlorine combine to give magnesium chloride.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-395-1024x819.png\" alt=\"\" class=\"wp-image-4271\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-395-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-395-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-395-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-395.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>14. Show the formation of cations of potassium (K) and calcium (Ca) atoms, and the formation of their corresponding chlorides using diagrams.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-396-1024x819.png\" alt=\"\" class=\"wp-image-4274\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-396-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-396-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-396-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-396.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>15. Illustrate how sodium sulfide (Na<sub>2<\/sub>S) is formed.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-397-1024x683.png\" alt=\"\" class=\"wp-image-4275\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-397-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-397-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-397-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-397.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>16. Name the following:<\/strong><br><strong>(i) CO<sub>2<\/sub> <\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>(ii) NO<sub>2<\/sub><\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>(iii) SF<sub>6<\/sub><\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>(iv) PCl<sub>3<\/sub><\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-398-1024x683.png\" alt=\"\" class=\"wp-image-4276\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-398-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-398-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-398-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-398.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>17. Write the formula for the following:<br>(i) Sodium hydrogencarbonate<br>(ii) Sulfur dioxide<br>(iii) Ferric chloride<br>(iv) Cuprous oxide<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-399-1024x683.png\" alt=\"\" class=\"wp-image-4277\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-399-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-399-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-399-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-399.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>18. Write the formulae for the compounds formed from the following pairs of ions:<br>(i) Fe<sup>3+<\/sup> and OH<sup>&#8210;<\/sup><br>(ii) K<sup>+<\/sup> and CO<sub>3<\/sub><sup>2-<\/sup><\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-400-1024x819.png\" alt=\"\" class=\"wp-image-4278\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-400-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-400-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-400-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-400.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>19. What type of chemical bond is present in a solid compound that does not conduct electricity in the solid state but conducts electricity when dissolved in water?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-401-1024x819.png\" alt=\"\" class=\"wp-image-4279\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-401-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-401-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-401-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-401.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>20. Metal M, with two electrons in its valence shell (M shell), reacts with oxygen to form a compound that is slightly soluble in water. Predict its:<br>(i) formula<br>(ii) type of bond<br>(iii) electrical conductivity of its aqueous solution.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-402-1024x683.png\" alt=\"\" class=\"wp-image-4280\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-402-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-402-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-402-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-402.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>21. Find the molecular mass of nitric acid (HNO<sub>3<\/sub>).<br>Atomic mass &mdash; H = 1 u; N = 14 u; O = 16 u.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-403-1024x819.png\" alt=\"\" class=\"wp-image-4283\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-403-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-403-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-403-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-403.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>22. Find the molecular mass of methane (CH<sub>4<\/sub>).<br>Atomic mass &mdash; C = 12 u; H = 1 u.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-404-1024x819.png\" alt=\"\" class=\"wp-image-4284\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-404-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-404-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-404-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-404.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>23. Find the formula unit mass of potassium chloride (KCl).<br>Atomic mass&thinsp;&mdash;&thinsp;K = 39 u; Cl = 35.5 u.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-405-1024x683.png\" alt=\"\" class=\"wp-image-4303\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-405-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-405-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-405-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-405-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-405.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>24. Find the formula unit mass of magnesium hydroxide, Mg(OH)<sub>2<\/sub>.<br>Atomic mass &mdash; Mg = 24 u; O = 16 u; H = 1 u<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-406-1024x819.png\" alt=\"\" class=\"wp-image-4306\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-406-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-406-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-406-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-406.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-luminous-vivid-orange-color has-text-color has-link-color has-x-large-font-size wp-elements-3 wp-block-paragraph\"><strong>Revise, Reflect, Refine<\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>1. A particular element (A) has one electron in its third shell. There is another element (B) with six electrons in its second shell.<br>(i) How many electrons does A tend to give or take to become stable?<br>(ii) What kind of ion would it form?<br>(iii) How many electrons does B tend to give or take to become stable?<br>(iv) What kind of ion would it form?<br>(v) If A and B were to combine, what kind of bond would be formed?<br>(vi) What would be the formula for the compound thus formed?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"879\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-407-1024x879.png\" alt=\"\" class=\"wp-image-4309\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-407-1024x879.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-407-300x257.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-407-768x659.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-407.png 1354w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>2. An element X has six electrons in its outer shell and forms a diatomic molecule.<br>(i) Why would that be so?<br>(ii) What kind of bond would it form?<br>(iii) Draw the structure of the molecule it would form.<br>(iv) A certain other element Y has two electrons in its second shell.<br>Draw the structure of the molecule that X would form with Y.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-408-1024x819.png\" alt=\"\" class=\"wp-image-4312\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-408-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-408-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-408-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-408.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>3. You want to design a new ionic compound, where the total positive charge is 6<sup>+<\/sup> and the total negative charge is 6&thinsp;<sup>&ndash;<\/sup>. Which of the following combinations gives the correct number of ions?<br>(i) 2 Al<sup>3+<\/sup> and 3 Cl<sup>&ndash;<\/sup><br>(ii) 3 Mg<sup>2+<\/sup> and 1 PO<sub>4<\/sub><sup>3-<\/sup><br>(iii) 2 Fe<sup>3+<\/sup> and 3 O<sup>2-<\/sup><br>(iv) 3 Ca<sup>2+<\/sup> and 2 SO<sub>4<\/sub><sup>2-<\/sup><br><\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-409-1024x683.png\" alt=\"\" class=\"wp-image-4313\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-409-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-409-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-409-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-409-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-409.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>4. Choose the correct statement(s) and correct the false statement(s).<br>(i) Elements are made up of molecules and compounds are made up of atoms.<br>(ii) The molecule of a compound is always made up of two or more atoms of the same kind.<br>(iii) One molecule of nitrogen gas contains three nitrogen atoms.<br>(iv) Water is made of two hydrogen atoms, covalently bonded with one oxygen atom.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-410-1024x819.png\" alt=\"\" class=\"wp-image-4314\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-410-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-410-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-410-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-410.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>5. Write the chemical formulae for the following compounds.<br>(i) Aluminium nitrate (ii) Calcium oxide (iii) Ferric oxide<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-411-1024x683.png\" alt=\"\" class=\"wp-image-4315\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-411-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-411-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-411-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-411-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-411.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>6. Write the formulae of the compounds formed from the following pairs of ions.<br>(i) Ca<sup>2+<\/sup> and Br<sup>&ndash;<\/sup><br>(ii) Al<sup>3+<\/sup> and CO<sub>3<\/sub><sup>2-<\/sup><br>(iii) K<sup>+<\/sup> and SO<sub>4<\/sub><sup>2-<\/sup><br>(iv) NH<sub>4<\/sub><sup>+<\/sup> and Cl<sup>&ndash;<\/sup><\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"896\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-412-1024x896.png\" alt=\"\" class=\"wp-image-4316\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-412-1024x896.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-412-300x262.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-412-768x672.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-412.png 1341w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>7. Which of the following, in Fig. 9.18, correctly represents Cl<sup>&ndash;<\/sup> ion (Atomic number of chlorine = 17).<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-413-1024x683.png\" alt=\"\" class=\"wp-image-4317\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-413-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-413-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-413-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-413-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-413.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>8. Determine the formula unit mass of the following substances. <br>(i) Ammonium nitrate (NH<sub>4<\/sub>NO<sub>3<\/sub>), used as a nitrogen fertiliser, which is essential for plant<\/strong> <strong>growth.<br>(ii) Phosphoric acid (H<sub>3<\/sub>PO<sub>4<\/sub>), used to make phosphate fertiliser and detergents.<br>(iii) Sodium hydrogencarbonate (NaHCO<sub>3<\/sub>), used to relieve acidity and helps in digestion.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"562\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-414-1024x562.png\" alt=\"\" class=\"wp-image-4318\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-414-1024x562.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-414-300x165.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-414-768x421.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-414-1536x843.png 1536w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-414.png 1693w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>9. Write the formulae for the compounds formed by the reaction of:<br>(i) Magnesium and nitrogen (ii) Lithium and nitrogen<br>(iii) Sodium and sulfur (iv) Aluminium and oxygen<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-415-1024x819.png\" alt=\"\" class=\"wp-image-4319\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-415-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-415-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-415-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-415.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>10. Complete the Table 9.3 by writing the formulae of the compounds formed by the cations on the left and the anions at the top. LiNO<sub>3<\/sub> is given as an example.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"526\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-416-1024x526.png\" alt=\"\" class=\"wp-image-4322\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-416-1024x526.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-416-300x154.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-416-768x395.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-416-1536x789.png 1536w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-416.png 1750w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>11. 5.3 g of sodium carbonate and 6.0 g of acetic acid react to produce 2.2 g of carbon dioxide, 0.9 g of water, and 8.2 g of sodium acetate. Verify whether the law of conservation of mass is valid.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-417-1024x683.png\" alt=\"\" class=\"wp-image-4323\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-417-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-417-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-417-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-417-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-417.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>12. If a species has 11 protons, 12 neutrons and 10 electrons then<br>(i) what is its atomic number and mass number?<br>(ii) is it neutral, a cation or an anion? Explain.<br>(iii) write its electronic configuration.<br>(iv) name the species.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-419-1024x683.png\" alt=\"\" class=\"wp-image-4325\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-419-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-419-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-419-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-419-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-419.png 1535w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>13. Two elements, A and B, have the following configurations&thinsp;&mdash;<br>A: 2, 8, 5                       B: 2, 8, 7<br>(i) Which element is more reactive?<br>(ii) Will A and B form ionic or covalent bonds when they combine? Explain using electron transfer or sharing.<br>(iii) Predict the formula of the compound they would form.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-418-1024x683.png\" alt=\"\" class=\"wp-image-4324\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-418-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-418-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-418-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-418-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-418.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>14. Assertion (A): Copper sulfate conducts electricity in the molten state but not in the solid state.<br>Reason (R): Copper and sulfate ions are fixed in the lattice in molten state, while in solid state they can move freely.<br>Choose the correct option:<br>(i) Both A and R are true, and R is the correct explanation of A.<br>(ii) Both A and R are true, but R is not the correct explanation of A.<br>(iii) A is true, but R is false.<br>(iv) A is false, but R is true.<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"683\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-420-1024x683.png\" alt=\"\" class=\"wp-image-4326\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-420-1024x683.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-420-300x200.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-420-768x512.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-420-1200x800.png 1200w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-420.png 1536w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>15. The species <sup>27<\/sup>Al, <sup>80<\/sup>Br<sup>&ndash;<\/sup> and <sup>201<\/sup>Hg<sup>2+<\/sup> have 13, 35 and 80 protons, respectively. How many electrons and neutrons do they have?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-421-1024x819.png\" alt=\"\" class=\"wp-image-4327\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-421-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-421-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-421-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-421.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<p class=\"has-luminous-vivid-orange-color has-text-color has-link-color has-x-large-font-size wp-elements-4 wp-block-paragraph\"><strong>The Quest Continues<\/strong><\/p>\n\n\n\n<p class=\"has-medium-font-size wp-block-paragraph\"><strong>1. Are there any chemical changes that do not obey the Law of Conservation of Mass?<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-image size-large\"><img loading=\"lazy\" decoding=\"async\" width=\"1024\" height=\"819\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-422-1024x819.png\" alt=\"\" class=\"wp-image-4328\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-422-1024x819.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-422-300x240.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-422-768x615.png 768w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/image-422.png 1402w\" sizes=\"(max-width: 1024px) 100vw, 1024px\"><\/figure>\n\n\n\n<h1 class=\"wp-block-heading\">Common Mistakes<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Confusing ionic and covalent bonds<\/li>\n\n\n\n<li>Writing wrong electronic configurations<\/li>\n\n\n\n<li>Forgetting brackets in polyatomic ions<\/li>\n\n\n\n<li>Ignoring charge balancing while writing formulae<\/li>\n\n\n\n<li>Incorrect molecular mass calculations<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Exam Tips<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Learn valencies of common ions.<\/li>\n\n\n\n<li>Practice criss-cross method regularly.<\/li>\n\n\n\n<li>Remember definitions of cation and anion.<\/li>\n\n\n\n<li>Draw bonding diagrams neatly.<\/li>\n\n\n\n<li>Revise important laws carefully.<\/li>\n<\/ul>\n\n\n\n<h1 class=\"wp-block-heading\">Practice MCQs<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">1. Which bond is formed by sharing electrons?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Ionic Bond<br>B. Covalent Bond<br>C. Metallic Bond<br>D. Hydrogen Bond<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Covalent Bond<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h3 class=\"wp-block-heading\">2. Which particle is positively charged?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Electron<br>B. Neutron<br>C. Proton<br>D. Atom<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. Proton<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h3 class=\"wp-block-heading\">3. Formula of magnesium oxide:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Mg&#8322;O<br>B. MgO&#8322;<br>C. MgO<br>D. Mg&#8322;O&#8322;<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. MgO<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h3 class=\"wp-block-heading\">4. Compound conducting electricity in aqueous solution is generally:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Covalent<br>B. Ionic<br>C. Organic<br>D. Neutral<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Ionic<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\">\n\n\n\n<h3 class=\"wp-block-heading\">5. Molecular mass of water:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. 16 u<br>B. 17 u<br>C. 18 u<br>D. 20 u<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. 18 u<\/p>\n\n\n\n<h1 class=\"wp-block-heading\">FAQ Section<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Q1. What is a covalent bond?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A bond formed by sharing electrons between atoms.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q2. What is an ionic bond?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A bond formed due to transfer of electrons and electrostatic attraction between ions.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q3. Why do ionic compounds conduct electricity in water?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Because ions become free to move in solution.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q4. What is molecular mass?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Sum of atomic masses of all atoms in a molecule.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q5. What is formula unit mass?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Mass of simplest ratio of ions in an ionic compound.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Master Chemistry concepts with detailed notes, solved questions, MCQs, quizzes, and mock tests only on <a href=\"http:\/\/www.mymockmate.com\/\">www.mymockmate.com<\/a> and improve your exam performance today!<\/p>\n\n\n \n<div data-block=\"gutenkit\/dual-button\" data-post-id=\"2521\" id=\"block-30666e02-fc71-4022-ac63-efd0309309c9\" class=\"wp-block-gutenkit-dual-button gkit-dual-button-middle-text gkit9309c9 gutenkit-block\"><div class=\"gkit-dual-btn-container\"><div class=\"gkit-dual-btn-wrapper\"><a class=\"gkit-dual-btn gkit-dual-btn-first\" href=\"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-journey-inside-the-atom-question-answers\/\"><span class=\"gkit-dual-btn-text\">&lt;&lt; Chapter 8<\/span><\/a><span class=\"gkit-dual-btn-middle-text\">Or<\/span><a class=\"gkit-dual-btn gkit-dual-btn-second\" href=\"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-sound-waves-characteristics-and-applications-solutions\/\"><span class=\"gkit-dual-btn-text\">Chapter 10 &gt;&gt;<\/span><\/a><\/div><\/div><\/div>\n \n\n\n<p class=\"wp-block-paragraph\"><\/p>\n<div class=\"mymoc-bottom mymoc-entity-placement\" id=\"mymoc-3295195614\"><div id=\"mymoc-16003872\"><a href=\"https:\/\/amzn.to\/4v5gV6P\" aria-label=\"calculators\"><img src=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/calculators.png\" alt=\"\" srcset=\"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/calculators.png 1302w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/calculators-300x99.png 300w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/calculators-1024x338.png 1024w, https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/06\/calculators-768x254.png 768w\" sizes=\"(max-width: 1302px) 100vw, 1302px\" width=\"1302\" height=\"430\"><\/a><\/div><\/div>","protected":false},"excerpt":{"rendered":"<p>Short Intro This chapter introduces the atomic nature of matter and explains how atoms combine to form molecules and compounds. Students learn important laws of&#8230;<\/p>\n","protected":false},"author":3,"featured_media":2524,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"postBodyCss":"","postBodyMargin":[],"postBodyPadding":[],"postBodyBackground":{"backgroundType":"classic","gradient":""},"footnotes":""},"categories":[4,12],"tags":[1380,1381,1382,1385,1383,1386,1384,1387],"class_list":["post-2521","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-class-9","category-science","tag-atomic-foundations-of-matter","tag-chemical-bonding","tag-covalent-bond","tag-dalton-atomic-theory","tag-ionic-bond","tag-law-of-conservation-of-mass","tag-law-of-constant-proportions","tag-molecular-mass"],"featured_image_src":"https:\/\/mymockmate.com\/notes\/wp-content\/uploads\/2026\/05\/NCERT-Class-9-Science-Atomic-Foundations-of-Matter-Solutions.png","author_info":{"display_name":"Team Mymockmate (L)","author_link":"https:\/\/mymockmate.com\/notes\/author\/luckp\/"},"_links":{"self":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2521","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/comments?post=2521"}],"version-history":[{"count":15,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2521\/revisions"}],"predecessor-version":[{"id":6800,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2521\/revisions\/6800"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media\/2524"}],"wp:attachment":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media?parent=2521"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/categories?post=2521"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/tags?post=2521"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}