Write a short note on the anomalous behavior of oxygen.

(N/A) The anomalous behavior of oxygen compared to other members of the $p$-block in the second period is primarily due to its small size and high electronegativity.
$A$ significant consequence of its small size and high electronegativity is the presence of strong hydrogen bonding in $H_2O$,which is not observed in $H_2S$.
Due to the absence of $d$-orbitals in oxygen,its covalency is limited to $4$,and in practice,it is rarely more than $2$. In contrast,other elements of the group can expand their valence shells,allowing for a covalency greater than $4$.