Make the idea your own
- 1Read the inputs and predict what will change.
- 2Change one parameter while keeping the other fixed.
- 3Explain the result using the diagram and the live values.
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Class 9 · Chemistry
Atomic structure
Interactive explanation Gamified quiz, feedback & rewards
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NCERT chapter connection · Learning goals & preparation
By the end, you can…
- Explain Mass number A = protons + neutrons
- Change one input at a time and predict its effect before checking the model.
- Apply the relationship in a quiz and explain the reasoning behind your answer.
Useful preparation: Counting particles, ratios and the difference between a model and a real substance. Suggested previous stop: Design a particle filter.
Exploration · Journey Inside the Atom
NCERT ePathshala current chapter index · checked 12 Nov 2026. This activity explores part of the chapter; it does not replace the textbook. Open official NCERT reference ↗
Interactive exploration · Class 9
Atomic structure
Class 9
CLASS 9 · CONCEPT QUEST
Turn understanding into a small adventureAtomic structure
Discover the rule, predict what happens, then put the idea to work.
DiscoverFind the idea→PredictThink it through→ApplyMake it click
3 rounds · no timer · up to 100 XP for your best result
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The relationshipMass number A = protons + neutrons
Assemble carbon-12
Protons determine the element. Neutrons change its isotope. Electrons determine the charge. Particle dots are a schematic count, not real electron paths.
+
−
Protons: 1
Neutrons: 0
Electrons: 1
Mass number: 1 · Net charge: 0
Build a neutral carbon-12 atom: 6 protons, 6 neutrons and 6 electrons.
Practice freely here. Your quiz stars are earned in the concept quest.
Notice the pattern
Isotopes have the same proton number and different neutron numbers. Some combinations shown are unstable or unbound.