nitrogen differs from the rest of the elements of the group. Like carbon, the nitrogen can from multiple bonds (N=N, C=N, N=O etc...). Nitrogen is a diatomic gas unlike the other members of the group. Similarly in group , the first element, oxygen also exists as a diatomic gas in that group.
Due to its high electronegativity it forms hydrogen bonds. The first element of group , fluorine the most electronegative element, also behaves quiet differently compared to the rest of the members of group. Like oxygen it also forms hydrogen bonds. It shows only - oxidation state while the other halogens have + , + , + and + oxidation states in addition to - state.
The fluorine is the strongest oxidising agent and the most reactive element among the halogens. . . Inert pair effect: We have already learnt that the alkali and alkaline earth metals have an oxidation state of + and + respectively, corresponding to the total number of electrons present in them.
Similarly, the elements of p-block also show the oxidation states corresponding to the maximum number of valence electrons (group oxidation state). In addition they also show variable oxidation state. In case of the heavier post-transition elements belonging to the groups ( to ), the most stable oxidation state is two less than the group oxidation state and there is a reluctance to exhibit the group oxidation state. Let us consider group elements.
As we move from boron to heavier elements, there is an increasing tendency to have + oxidation state, rather than the group oxidation state, + . For example Al + is more stable than Al + while Tl + is more stable than Tl + . Aluminium(III)chloride is stable whereas thallium(III)chloride is highly unstable and disproportionates to thallium(I) chloride and chlorine gas. This shows that in thallium the stable lower oxidation state corresponds to the loss of np electrons only and not ns electrons.
Thus in heavier post- transition metals, the outer s electrons (ns) have a tendency to remain inert and show reluctance to take part in the bonding, which is known as