In this chapter, the following topics are important for long questions in board exams:

1. Subatomic Particles (Protons, Neutrons, Electrons)

Describe protons, neutrons, and electrons in terms of their relative masses, charges, and locations in the atom. Explain how these particles were discovered and their significance.

2. Atomic and Mass Number

Explain the terms atomic number (proton number) and mass number (nucleon number). Show how to determine the number of protons, neutrons, and electrons in atoms and ions from atomic number and mass number.

3. Behaviour of Particles in an Electric Field

Describe the behaviour of beams of protons, neutrons, and electrons moving at the same velocity in an electric field. Explain why protons and electrons deflect in opposite directions while neutrons do not deflect.

4. Quantum Numbers and Electronic Distribution

Relate quantum numbers (n, l, m, s) to the electronic distribution of elements. Explain the principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (m), and spin quantum number (s).

5. Shells, Sub-shells, and Orbitals

Define shells, sub-shells, and orbitals. Describe the order of increasing energy of sub-shells (s, p, d, f). Explain that each shell and sub-shell is divided into degenerate orbitals (orbitals with the same energy).

6. Rules for Electronic Configuration (Aufbau, Pauli, Hund)

Explain and apply the Aufbau principle, Pauli’s exclusion principle, and Hund’s rule to write the electronic configuration of elements. Give examples of how these rules work.

7. Shapes of Orbitals

Describe the shapes of s, p, and d orbitals. Explain why s orbitals are spherical, p orbitals are dumbbell-shaped, and d orbitals have more complex shapes.

8. Electronic Configuration of Atoms and Ions

Determine the electronic configuration of elements and their ions (including both simple configuration like 2, 8 and sub-shell configuration like 1s² 2s² 2p⁶). Explain how to find these from the periodic table.

9. Successive Ionization Energies

Explain the variation in successive ionization energies of an element. Show how ionization energy data can be used to deduce the electronic configuration and position of an element in the periodic table.

10. Factors Influencing Ionization Energy

Explain the factors influencing ionization energy: nuclear charge, atomic/ionic radius, shielding effect, sub-shell occupancy, and spin-pair repulsion. Explain how these factors affect trends across a period and down a group.

11. Trends in Atomic and Ionic Radius

Explain the change in atomic and ionic radius across a period and down a group. Justify why atomic radius decreases across a period but increases down a group.

12. Free Radicals

Describe a free radical as a species with one or more unpaired electrons. Explain their significance in chemical reactions.

13. Electronic Configurations and New Materials

Illustrate the importance of electronic configurations in the development of new materials for electronic devices. Explain why semiconductors like silicon have specific configurations that make them ideal for electronic devices.