Question

The first element of all the groups show anomalous behaviour why?

Answer 1

the first members of each group of representative elements shows anomalous behaviour because:
1. small size
2. high ionisation enthalpy
3.high electronegativity

4. absence of d- orbitals

Answer 2

The first element of all the groups show anomalous behavior because of the following reasons:

1. High Electronegativity: The electronegativity of an element decreases down the group. Due to this, the first element of a group is more electronegative.
2. Small Size: The size of an atom increases down the group due to the addition of new shells. Smaller atoms react differently than atoms of larger size.
3. Absence of d-orbitals: The first period elements do not have d-orbitals. Thus they cannot expand their valency like their subsequent group members.