NCERT Class 9 Science Exploration: Chapter 8 — 8. Journey Inside the Atom
This chapter, 'The Atom,' from NCERT Class 9 Science Exploration, delves into the fundamental building blocks of matter. It begins by establishing that everything around us, living or non-living, is composed of atoms, which are incredibly tiny particles. The chapter traces the historical evolution of atomic theory, starting from ancient Indian philosopher Acharya Kanada's concept of 'parmanus' and Greek philosophers Leucippus and Democritus's 'atomos,' both suggesting indivisible particles. It then highlights John Dalton's atomic theory in 1808 as the first scientific description of atoms as fundamental, indivisible units of matter. The text also poses key questions about atomic structure and the divisibility of atoms, setting the stage for understanding how scientific models of the atom have evolved over time through experimentation and new evidence, driven by curiosity and questioning. This exploration is crucial for understanding the basis of chemistry and physics.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 9 |
| Subject | Science |
| Book | Exploration |
| Chapter | Chapter 8 — 8. Journey Inside the Atom |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 2 minutes |
| Word count | 344 |
Learning outcomes
- Understand that all matter is composed of atoms.
- Trace the historical development of atomic theory from ancient India and Greece to John Dalton.
- Recognize atoms as fundamental building blocks of matter.
- Appreciate the role of curiosity and experimentation in scientific progress.
- Understand that atomic models have evolved over time.
Vocabulary
| Word | Meaning |
|---|---|
| Matter | Anything that has mass and occupies space. |
| Atom | The smallest indivisible particle of an element. |
| Parmanu | The smallest indivisible particle according to Acharya Kanada. |
| Atomos | Indivisible particle in Greek philosophy. |
| Atomic Theory | A scientific description of how matter is made up of atoms. |
| Radiation | Invisible energy and particles emitted by certain elements. |
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Practice questions
- What did Acharya Kanada suggest about matter? Answer: Acharya Kanada suggested that if matter is divided repeatedly, one reaches the smallest indivisible particles called parmanus.
- What did the Greek philosophers Leucippus and Democritus call the indivisible particles? Answer: They called these indivisible particles atomos.
- Who proposed the first scientific atomic theory and when? Answer: John Dalton proposed his atomic theory in 1808.
- According to Dalton's atomic theory, what are atoms? Answer: According to Dalton's atomic theory, atoms are the fundamental building blocks of matter that cannot be broken down into smaller parts.
Frequently asked questions
What is matter made of?
Matter is made up of tiny particles called atoms.
Were atoms always considered divisible?
No, initially, atoms were thought to be the smallest, indivisible units of matter, a concept originating from ancient Indian and Greek philosophers and later proposed by John Dalton.
What was the contribution of Acharya Kanada?
Acharya Kanada suggested that matter, when divided repeatedly, leads to the smallest indivisible particles called 'parmanus'.
What does 'atomos' mean?
'Atomos' is a Greek word meaning indivisible.
When was the first scientific atomic theory proposed?
The first scientific atomic theory was proposed by John Dalton in 1808.
Why are early atomic models still important?
Early atomic models are important because they show how science progresses through curiosity, questioning, and experimentation, even if they were not fully correct.
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NCERT Class 9 Science — Exploration — Chapter 8 — 8. Journey Inside the Atom. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.