Question

Why are oxygen and hydrogen diatomic?

Answer 1

Hint :Pure elements that form molecules consisting of two atoms are called diatomic elements. There are seven diatomic elements. They are hydrogen, oxygen, nitrogen, fluorine, chlorine, iodine and bromine. Diatomic molecules do not like to be alone.

Complete Step By Step Answer:
Oxygen exists as a diatomic molecule in nature when it is not combined with any other element. It forms $ {O_2} $ molecule because it is stable when it is uncombined. It has the lowest energy level when uncombined. Remember that stability is inversely proportional to energy. Hydrogen exists as a diatomic molecule in nature when it is not combined with any other element. It forms $ {H_2} $ molecule because it is stable when it is uncombined. It has the lowest energy level when uncombined. Observe that diatomic elements are mostly halogens because they have one unpaired electron in the valence shell. In order to achieve the octet configuration, they share their unpaired electron with the unpaired electron of another element and result in a diatomic molecule. By achieving octet configuration, the diatomic elements become more stable compared to the single atom.
Therefore, oxygen and hydrogen are diatomic.

Note :
The molecules which have two atoms bonded chemically are called diatomic molecules. If the two atoms are the same, for example, hydrogen, it is called a homonuclear diatomic molecule. Hydrogen has one electron less than stable inert gas configuration. So, it shares that electron with another hydrogen atom and forms a diatomic molecule which is stable.