{"id":2515,"date":"2026-05-28T17:13:55","date_gmt":"2026-05-28T11:43:55","guid":{"rendered":"https:\/\/mymockmate.com\/notes\/?p=2515"},"modified":"2026-05-28T17:13:59","modified_gmt":"2026-05-28T11:43:59","slug":"ncert-class-9-science-journey-inside-the-atom-question-answers","status":"publish","type":"post","link":"https:\/\/mymockmate.com\/notes\/ncert-class-9-science-journey-inside-the-atom-question-answers\/","title":{"rendered":"NCERT  Class 9 Science Journey Inside the Atom  Question Answers"},"content":{"rendered":"<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2515?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\" ><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\" \/><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">1<\/span><\/div>\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h1 class=\"wp-block-heading\">Short Intro<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">This chapter explains the fascinating journey of discovering the structure of the atom. Students learn about atomic models proposed by Dalton, Thomson, Rutherford, and Bohr along with concepts such as atomic number, mass number, isotopes, isobars, electronic configuration, and valency.<\/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 Name<\/td><td>Journey Inside the Atom<\/td><\/tr><tr><td>Class<\/td><td>Grade 9<\/td><\/tr><tr><td>Subject<\/td><td>Science<\/td><\/tr><tr><td>Main Concepts<\/td><td>Atomic Models, Electrons, Protons, Neutrons<\/td><\/tr><tr><td>Important Scientist<\/td><td>Rutherford, Bohr, Chadwick<\/td><\/tr><tr><td>Key Formula<\/td><td>Mass Number = Protons + Neutrons<\/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>Dalton\u2019s Atomic Theory<\/li>\n\n\n\n<li>Thomson\u2019s Plum Pudding Model<\/li>\n\n\n\n<li>Rutherford\u2019s Gold Foil Experiment<\/li>\n\n\n\n<li>Bohr\u2019s Atomic Model<\/li>\n\n\n\n<li>Discovery of Electron, Proton and Neutron<\/li>\n\n\n\n<li>Atomic Number and Mass Number<\/li>\n\n\n\n<li>Electronic Configuration<\/li>\n\n\n\n<li>Valency<\/li>\n\n\n\n<li>Isotopes and Isobars<\/li>\n\n\n\n<li>Average Atomic 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>Atomic Number<br>Z = Number of Protons<\/li>\n\n\n\n<li>Mass Number<br>A = Number of Protons + Number of Neutrons<\/li>\n\n\n\n<li>Number of Neutrons<br>Neutrons = Mass Number \u2212 Atomic Number<\/li>\n\n\n\n<li>Maximum Electrons in Shell<br>2n\u00b2<\/li>\n\n\n\n<li>Average Atomic Mass<br>Average Mass = \u03a3(Isotopic Mass \u00d7 Abundance)\/100<\/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<h1 class=\"wp-block-heading\">Q1. Rutherford Gold Foil Experiment<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) The experiment clearly showed the existence of neutrons in the nucleus.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Neutrons were discovered later by James Chadwick.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Incorrect<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) The results disproved the plum pudding model and led to the idea of nucleus.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Large deflections proved positive charge is concentrated in nucleus.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Correct<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Large deflection of alpha particles showed most mass is concentrated in tiny nucleus.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Only a dense nucleus can strongly deflect alpha particles.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Correct<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) Deflection showed electrons move around nucleus.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Gold foil experiment mainly explained nucleus, not electron motion.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Incorrect<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q2. Bohr\u2019s Atomic Model<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Electrons lose energy in fixed orbits.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Incorrect<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Bohr said electrons do not lose energy in fixed orbits.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Electrons can exist anywhere around nucleus.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Incorrect<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrons revolve only in fixed energy levels.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Electrons revolve in fixed energy orbits without losing energy.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Correct<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) Electrons can exist between energy levels.<\/h3>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Incorrect<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Explanation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrons cannot stay between shells.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q3. Relation Between X, Y and Z<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Species<\/th><th>Protons<\/th><th>Neutrons<\/th><\/tr><\/thead><tbody><tr><td>X<\/td><td>18<\/td><td>19<\/td><\/tr><tr><td>Y<\/td><td>17<\/td><td>18<\/td><\/tr><tr><td>Z<\/td><td>17<\/td><td>20<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Relation between Y and Z<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Atomic numbers same but neutrons different.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Y and Z are isotopes.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Relation between Z and X<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Mass numbers:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Z = 17 + 20 = 37<\/li>\n\n\n\n<li>X = 18 + 19 = 37<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">Same mass number but different atomic number.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Z and X are isobars.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q4. Rutherford\u2019s Conclusion<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Rutherford concluded:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Positive charge is concentrated in a tiny nucleus.<\/li>\n\n\n\n<li>Most atom space is empty.<\/li>\n\n\n\n<li>Nucleus is dense and heavy.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q5. Chronological Order of Atomic Models<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Correct Order:<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Dalton\u2019s Model<\/li>\n\n\n\n<li>Thomson\u2019s Model<\/li>\n\n\n\n<li>Rutherford\u2019s Model<\/li>\n\n\n\n<li>Bohr\u2019s Model<\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q6. Why Electrons Do Not Fly Away<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrons are negatively charged and nucleus is positively charged.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Electrostatic force of attraction keeps electrons around nucleus.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q7. Assertion and Reason<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Assertion:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Discovery of subatomic particles helped understand atomic structure.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Reason:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Number of electrons equals number of protons.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">(ii) Both are true, but R is not correct explanation of A.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q8. Magnesium Atom<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Given:<br>Atomic number = 12<br>Mass number = 24<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Protons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 12<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Neutrons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 24 \u2212 12 = 12<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Electrons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 12<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Electronic Configuration<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">2, 8, 2<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q9. Information About Elements<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(a)<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electronic configuration = 2,1<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Element = Lithium<\/li>\n\n\n\n<li>Symbol = Li<\/li>\n\n\n\n<li>Electrons = 3<\/li>\n\n\n\n<li>Valence electrons = 1<\/li>\n\n\n\n<li>Valency = 1<\/li>\n\n\n\n<li>Protons = 3<\/li>\n\n\n\n<li>Atomic number = 3<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(b)<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electronic configuration = 2,8<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Element = Neon<\/li>\n\n\n\n<li>Symbol = Ne<\/li>\n\n\n\n<li>Electrons = 10<\/li>\n\n\n\n<li>Valency = 0<\/li>\n\n\n\n<li>Protons = 10<\/li>\n\n\n\n<li>Atomic number = 10<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(c)<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electronic configuration = 2,8,1<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Element = Sodium<\/li>\n\n\n\n<li>Symbol = Na<\/li>\n\n\n\n<li>Valency = 1<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(d)<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electronic configuration = 2,8,7<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Element = Chlorine<\/li>\n\n\n\n<li>Symbol = Cl<\/li>\n\n\n\n<li>Valency = 1<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q10. Rutherford vs Bohr Model<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Rutherford\u2019s Limitation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrons revolving around nucleus should lose energy and collapse.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Bohr\u2019s Explanation:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Electrons move in fixed energy levels without losing energy.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q11. Atom \u2077\u2070X with 31 Electrons<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">Solution:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Atomic number = 31<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Neutrons = 70 \u2212 31<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 39<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">39 neutrons<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q12. Atom with 79 Protons and Mass Number 197<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Neutrons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 197 \u2212 79<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">= 118<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Electrons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 79<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q13. Complete the Table<\/h1>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><thead><tr><th>Atomic Number<\/th><th>Mass Number<\/th><th>Neutrons<\/th><th>Protons<\/th><th>Electrons<\/th><th>Element<\/th><\/tr><\/thead><tbody><tr><td>5<\/td><td>11<\/td><td>6<\/td><td>5<\/td><td>5<\/td><td>Boron<\/td><\/tr><tr><td>7<\/td><td>14<\/td><td>7<\/td><td>7<\/td><td>7<\/td><td>Nitrogen<\/td><\/tr><tr><td>12<\/td><td>24<\/td><td>12<\/td><td>12<\/td><td>12<\/td><td>Magnesium<\/td><\/tr><tr><td>15<\/td><td>31<\/td><td>16<\/td><td>15<\/td><td>15<\/td><td>Phosphorus<\/td><\/tr><tr><td>1<\/td><td>1<\/td><td>0<\/td><td>1<\/td><td>1<\/td><td>Hydrogen<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q14. Element X<\/h1>\n\n\n\n<p class=\"wp-block-paragraph\">Given:<br>Mass number = 35<br>Neutrons = 18<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Protons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 35 \u2212 18 = 17<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Electrons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">= 17<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Atomic Number<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">17<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Element<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Chlorine<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) Electronic Configuration<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">2, 8, 7<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(v) Valence Electrons<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">7<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(vi) New Mass Number<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">35 + 2 = 37<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">(vii) Relation with New Atom<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">They are isotopes.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Q15. Hypothetical Heavy Electrons<\/h1>\n\n\n\n<h3 class=\"wp-block-heading\">(i) Atomic Number<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No change<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(ii) Atomic Mass<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Increases<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(iii) Mass Number<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">No change<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">(iv) Overall Charge<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Neutral<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading\">Common Mistakes<\/h1>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Confusing atomic number with mass number<\/li>\n\n\n\n<li>Forgetting neutrons calculation<\/li>\n\n\n\n<li>Writing incorrect shell capacities<\/li>\n\n\n\n<li>Mixing isotopes and isobars<\/li>\n\n\n\n<li>Incorrect electronic configuration<\/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 all atomic models in sequence.<\/li>\n\n\n\n<li>Practice electron distribution regularly.<\/li>\n\n\n\n<li>Remember formulas for atomic number and mass number.<\/li>\n\n\n\n<li>Revise isotopes and isobars carefully.<\/li>\n\n\n\n<li>Draw neat atomic diagrams in exams.<\/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. Who discovered the nucleus?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Dalton<br>B. Rutherford<br>C. Bohr<br>D. Chadwick<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Rutherford<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">2. Maximum electrons in K-shell:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. 8<br>B. 18<br>C. 2<br>D. 32<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. 2<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">3. Atomic number equals:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Neutrons<br>B. Electrons + Neutrons<br>C. Protons<br>D. Mass number<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. Protons<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">4. Isotopes have:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Same mass number<br>B. Same atomic number<br>C. Different electrons only<br>D. Same neutrons<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">B. Same atomic number<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">5. Scientist who discovered neutron:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">A. Bohr<br>B. Rutherford<br>C. Chadwick<br>D. Thomson<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Answer:<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">C. Chadwick<\/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 atomic number?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Atomic number is the number of protons in an atom.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q2. What is mass number?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Mass number is total number of protons and neutrons.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q3. What are isotopes?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Atoms with same atomic number but different mass numbers.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q4. What are isobars?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Atoms with same mass number but different atomic numbers.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">Q5. Why are noble gases stable?<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Because they have complete outermost electron shells.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Prepare smarter with chapter-wise notes, solved questions, MCQs, quizzes, and mock tests only on <a href=\"http:\/\/www.mymockmate.com\/\">www.mymockmate.com<\/a> and boost your exam performance today!<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n<div class=\"pdfprnt-buttons pdfprnt-buttons-post pdfprnt-top-bottom-right\"><a href=\"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2515?print=print\" class=\"pdfprnt-button pdfprnt-button-print\" target=\"_blank\" ><img decoding=\"async\" src=\"https:\/\/mymockmate.com\/notes\/wp-content\/plugins\/pdf-print\/images\/print.png\" alt=\"image_print\" title=\"Print Content\" \/><span class=\"pdfprnt-button-title pdfprnt-button-print-title\">Print<\/span><\/a> <span class=\"pdfprnt-count-generation\">1<\/span><\/div>\n    <div class=\"xs_social_share_widget xs_share_url after_content \t\tmain_content  wslu-style-1 wslu-share-box-shaped wslu-fill-colored wslu-none wslu-share-horizontal wslu-theme-font-no wslu-main_content\">\n\n\t\t\n        <ul>\n\t\t\t        <\/ul>\n    <\/div> \n","protected":false},"excerpt":{"rendered":"<p> 1 Short Intro This chapter explains the fascinating journey of discovering the structure of the atom. Students<\/p>\n","protected":false},"author":3,"featured_media":2518,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_surecart_dashboard_logo_width":"180px","_surecart_dashboard_show_logo":true,"_surecart_dashboard_navigation_orders":true,"_surecart_dashboard_navigation_invoices":true,"_surecart_dashboard_navigation_subscriptions":true,"_surecart_dashboard_navigation_downloads":true,"_surecart_dashboard_navigation_billing":true,"_surecart_dashboard_navigation_account":true,"postBodyCss":"","postBodyMargin":[],"postBodyPadding":[],"postBodyBackground":{"backgroundType":"classic","gradient":""},"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[22,4,12],"tags":[1365,1366,1363,1359,1368,1369,1367,1364,1370],"class_list":["post-2515","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-cbse","category-class-9","category-science","tag-atom-structure","tag-atomic-number","tag-bohr-model","tag-class-9-science","tag-isobars","tag-isotopes","tag-mass-number","tag-rutherford-model","tag-valency"],"jetpack_publicize_connections":[],"_links":{"self":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2515","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=2515"}],"version-history":[{"count":2,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2515\/revisions"}],"predecessor-version":[{"id":2650,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/posts\/2515\/revisions\/2650"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media\/2518"}],"wp:attachment":[{"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/media?parent=2515"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/categories?post=2515"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mymockmate.com\/notes\/wp-json\/wp\/v2\/tags?post=2515"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}