Atoms and Molecules Quiz - CBSE Class 9 Science

Free practice quiz: Atoms and Molecules (CBSE Class 9 Science). 18 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This CBSE Class 9 Science practice quiz has 18 multiple-choice questions on Atoms and Molecules, and 18 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. What is the smallest particle of an element that retains its chemical properties?

   1. Atom
   2. Molecule
   3. Compound
   4. Ion
   Show answer

   Answer: A. Atom

   An atom is the smallest particle of an element that retains the element's chemical properties.

2. Which of the following correctly represents the atomic composition of carbon dioxide?

   1. CO2
   2. C2O
   3. CO
   4. OC
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   Answer: A. CO2

   Carbon dioxide is composed of one carbon atom and two oxygen atoms, which is represented by the chemical formula CO2.

3. Which is a characteristic of chemical compounds?

   1. Fixed ratio of atoms
   2. Variable ratio of elements
   3. Only one type of atom
   4. Can be separated by physical means
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   Answer: A. Fixed ratio of atoms

   Chemical compounds have a fixed ratio of atoms of different elements, which define the compound's chemical formula.

4. Which term describes a molecule consisting of two atoms?

   1. Diatomic
   2. Monatomic
   3. Polyatomic
   4. Triatomic
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   Answer: A. Diatomic

   Diatomic refers to a molecule composed of two atoms, such as O2 or H2.

5. Which is the heaviest component of an atom in terms of mass?

   1. Neutron
   2. Proton
   3. Electron
   4. Quark
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   Answer: A. Neutron

   The neutron is slightly more massive than a proton and vastly more massive than an electron. Quarks are components of protons and neutrons.

More questions in this quiz

Answers and explanations are in the full quiz.

1. Which of the following is a molecule?
2. What is the molecular formula for water?
3. Who proposed the atomic theory that atoms cannot be created or destroyed in a chemical reaction?
4. What name is given to the positively charged center of an atom?
5. Which scientist is credited with the discovery of the proton?
6. According to Dalton's atomic theory, all atoms of a given element are...
7. What is the primary difference between atoms of different elements?
8. In which type of bond are electrons shared between atoms?
9. Which scientist first proposed the model of the atom with electrons distributed throughout a positive sphere?
10. What does Avogadro's number represent?
11. Identify the type of reaction: 2H2 + O2 → 2H2O
12. What distinguishes an isotope from the standard form of an element?
13. Predict the product of the following reaction: Na + Cl2 → ?

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