Short questions in board exams usually come from these topics:

1. What are protons, neutrons, and electrons?

Define each subatomic particle. Give their relative masses and charges.

2. What is atomic number?

Define atomic number (proton number). What does it represent?

3. What is mass number?

Define mass number (nucleon number). What does it represent?

4. How do you find the number of neutrons in an atom?

Explain the formula: Number of neutrons = Mass number – Atomic number.

5. What is the behaviour of protons in an electric field?

Protons are positively charged, so they are deflected towards the negative plate.

6. What is the behaviour of electrons in an electric field?

Electrons are negatively charged, so they are deflected towards the positive plate.

7. What is the behaviour of neutrons in an electric field?

Neutrons have no charge, so they are not deflected by an electric field.

8. What is a quantum number?

Define quantum number. Explain the principal quantum number (n) briefly.

9. What is a shell?

Define shell (energy level). What is the maximum number of electrons in a shell?

10. What is a sub-shell?

Define sub-shell. Name the four sub-shells (s, p, d, f).

11. What is an orbital?

Define orbital. What is the maximum number of electrons in an orbital? (2)

12. What is the Aufbau principle?

State the Aufbau principle: electrons fill the lowest energy orbitals first.

13. What is Pauli’s exclusion principle?

State Pauli’s exclusion principle: no two electrons in an atom can have the same four quantum numbers.

14. What is Hund’s rule?

State Hund’s rule: electrons fill degenerate orbitals singly first, before pairing.

15. What are degenerate orbitals?

Define degenerate orbitals: orbitals that have the same energy (e.g., 2p orbitals).

16. What is the shape of an s orbital?

s orbitals are spherical in shape.

17. What is the shape of a p orbital?

p orbitals are dumbbell-shaped.

18. What is ionization energy?

Define ionization energy: the energy required to remove an electron from a gaseous atom.

19. What is the trend in ionization energy across a period?

Ionization energy increases across a period due to increasing nuclear charge.

20. What is the trend in ionization energy down a group?

Ionization energy decreases down a group due to increasing atomic radius and shielding effect.

21. What is a free radical?

A free radical is a species with one or more unpaired electrons.

22. What is the shielding effect?

Define shielding effect: the inner electrons shield the outer electrons from the full attraction of the nucleus.

23. What is spin-pair repulsion?

Define spin-pair repulsion: the repulsion between two electrons in the same orbital.

24. Why do atomic radii decrease across a period?

Increasing nuclear charge pulls electrons closer to the nucleus, decreasing atomic radius.

25. Why do atomic radii increase down a group?

Additional shells increase the distance between the nucleus and outer electrons, increasing atomic radius.