Anomalous Behaviour of First Element in Each Group of The p-Block

The elements comprising s-block and p-block are called main groups or representative elements.

Since the atomic radii decrease across a period, the p-block atoms are smaller than their nearest s or d block atoms. Thus, F atom has the smallest radius.

The small size of the atoms of N, O and F results in their high electonegativity values. This is reflected in the formation of relatively strong hydrogen bonds.

Carbon, nitrogen and oxygen differ from other elements of their respective groups due to their unique ability to form pπ–pπ multiple bonds. The later members such as Si, P, S, etc. do not form pπ–pπ bonds because the atomic orbitals (3p) are too large to achieve effective overlapping.

The valence shell capacity of the p-block elements in the second period limits the coordination number to a maximum of 4. However, in compounds of the heavier members the higher coordination numbers are attainable.