Anomalous behaviour of oxygen

Oxygen shows the following anomalous properties compared to other members of group 16:

i. Atomicity : Oxygen is a diatomic molecule ($\mathrm{O_2}$) while the others form polyatomic molecules — sulfur, for example, exists as $\mathrm{S_8}$.

ii. Magnetic property : Oxygen is paramagnetic while the others are diamagnetic.

iii. Oxidation state : Oxygen shows −2, −1 and +2 oxidation states while the other elements show −2, +2, +4 and +6 oxidation states. Oxygen cannot exhibit higher oxidation states due to the absence of vacant d orbitals.

iv. Nature of hydrides : The hydride of oxygen ($\mathrm{H_2O}$) is a liquid at room temperature while the hydrides of the other members of the group are gases.

v. Common covalency of oxygen is 2. In rare cases it is four. But for the other members of group 16 the covalency can exceed four. …