Question

Why is oxygen called gas?

Answer 1

Hint: We know that oxygen is the element of group sixteen in the periodic table and oxygen is present at the second period of the periodic table. All the second period elements show some exceptional behavior from the rest of the group, because these second group elements are small in size. And they don’t have d-orbitals.

Complete answer:
In gaseous molecules the intermolecular forces are weak and hence the distance between each molecule is large in gaseous state, while in case of solid the intermolecular forces are strong and hence the distance between each molecule is very small, hence they have definite e structure. Here oxygen is small in size as compared to the sulphur molecule, so oxygen will have high electronegativity. Also oxygen does not have d-orbital in it, they have only p-orbital. Since the size is small, after forming a single bond oxygen-oxygen.
Oxygen remains in a gaseous state at normal temperature and pressure. It is a very reactive non-metal and forms oxides with other elements. They have low densities and can be compressed easily. As the property of gases having no shape and volume, oxygen does not have a fixed shape or volume. Oxygen flows from areas of higher to lower concentrations. Hence for these reasons oxygen remains as gas.
Therefore, Oxygen is called gas.

Note:
Remember that there is a large difference between the melting and boiling point of oxygen, and it can be explained on the basis of atomicity. As oxygen exists as a diatomic molecule in nature and sulphur exists as a polyatomic molecule. And the reason for different atomicity was explained.