General Science Important Questions Chapter 5 Inside the Atom Class 8 Maharashtra Board

Imp Questions For All Chapters – General Science Class 8

Short Questions

1. What is matter made of?

• Matter is made of atoms and molecules.

2. What is an atom?

• An atom is the smallest unit of an element that retains its properties.

3. Who discovered the electron?

• J.J. Thomson discovered the electron.

4. Where are protons and neutrons found in an atom?

• They are found in the nucleus of an atom.

5. What is the charge of a proton?

• A proton has a positive (+1) charge.

6. What is the charge of an electron?

• An electron has a negative (-1) charge.

7. What is the charge of a neutron?

• A neutron has no charge (neutral).

8. What is atomic number?

• Atomic number (Z) is the number of protons in an atom.

9. What is atomic mass number?

• Atomic mass number (A) is the total number of protons + neutrons in an atom.

10. What are isotopes?

• Isotopes are atoms of the same element with different mass numbers but the same atomic number.

11. What is valency?

• Valency is the number of bonds an atom can form to become stable.

12. What is Rutherford’s atomic model?

• Rutherford said that an atom has a small, dense nucleus with electrons revolving around it.

13. What is Bohr’s atomic model?

• Bohr said that electrons revolve in fixed orbits (shells) around the nucleus and do not lose energy.

14. What is a nuclear reactor?

• A machine that produces electricity using nuclear fission reactions.

15. What is the function of a moderator in a nuclear reactor?

• A moderator (heavy water or graphite) slows down neutrons to control nuclear reactions.

Long Questions

1. What is the difference between Thomson’s and Rutherford’s atomic models?

• Thomson’s Model: The atom is a sphere with positive charge spread everywhere and electrons embedded inside.
• Rutherford’s Model: The atom has a small nucleus with protons and electrons revolving around it in empty space.

2. How do electrons revolve around the nucleus in Bohr’s model?

• Bohr said that electrons move in fixed orbits (shells) at a certain distance from the nucleus.
• Each orbit has a specific energy, and electrons do not lose energy while moving in their orbit.

3. What is the difference between atomic number and mass number?

• Atomic number (Z) is the number of protons in an atom.
• Mass number (A) is the total number of protons + neutrons in an atom.

4. What are isotopes? Give an example.

• Isotopes are atoms of the same element with the same atomic number but different mass numbers.
• Example: Carbon has three isotopes – C-12, C-13, and C-14.

5. Why is an atom electrically neutral?

• An atom has equal numbers of protons (positive) and electrons (negative).
• Since positive and negative charges cancel each other, the atom remains neutral.

6. Why is Rutherford’s model not completely correct?

• According to physics, a charged particle (electron) moving in a circle should lose energy and fall into the nucleus.
• But atoms are stable, so Rutherford’s model could not explain this, which Bohr corrected later.

7. What happens in a nuclear reactor?

• A nuclear reactor uses uranium or thorium to produce energy through nuclear fission.
• The energy released is used to heat water, create steam, and generate electricity.

8. What are the main subatomic particles? Give their properties.

• Proton (+1 charge, in nucleus, mass = 1u)
• Neutron (neutral, in nucleus, mass = 1u)
• Electron (-1 charge, orbits nucleus, mass negligible)