(ii) Periodicity on the basis of atomic number forelements.  The study of modern periodic table up toperiod 3 (students to be exposed to thecomplete modern periodic table but noquestions will be asked on elementsbeyond period 3 – Argon);  Periodicity and other related propertiesto be explained on the basis of nuclearcharge and shells (not orbitals). (Special reference to the alkali metals and halogengroups)

(ii) Periodicity on the basis of atomic number for elements:

1. Start by studying the modern periodic table up to period 3. It is important to familiarize yourself with the elements in this range.

2. Understand that the periodic table is organized based on the atomic number of elements. The atomic number represents the number of protons in an atom's nucleus.

3. Notice that elements in the same period have the same number of electron shells. For example, all elements in period 1 have only one electron shell, while elements in period 2 have two electron shells, and so on.

4. Observe that elements in the same group or column have similar properties. Focus on the alkali metals (Group 1) and halogen groups (Group 17) as special references.

5. Explain the periodicity of elements based on their nuclear charge and electron shells. Elements with a higher nuclear charge tend to have more protons in their nucleus, which leads to stronger attraction for electrons and smaller atomic size.

6. Understand that elements in the same group have the same number of valence electrons, which determines their chemical reactivity. For example, alkali metals have one valence electron, making them highly reactive, while halogens have seven valence electrons and tend to gain one electron to achieve a stable electron configuration.

7. Remember that the periodic table provides a systematic way to organize and understand the properties of elements based on their atomic number, nuclear charge, and electron configuration.