Question

One gram molecule of oxygen represents:
A.One mole of O
B.One mole of ${O_2}$
C.One mole of ${O_3}$
D.None of these

Answer 1

Oxygen exists in the form of a gas in its free state. But before diving into the question, let us first understand some basic concepts. The atomic number of oxygen is 8. Hence, this means that there are 8 protons and 8 electrons in an oxygen. From this and by Aufbau’s Principle, we can say that Oxygen has an electronic configuration as follows: $1{s^2}2{s^2}2{p^4}$.

Complete step by step answer:
This shows us that there are only 4 electrons present in the valence subshell, i.e. 2p. This means that the valence orbital is only partially filled, which in turn reduces the stability of the atom. To increase its stability, oxygen atom forms pi- pi bonds with itself thus satisfying the outer electronic configuration of the oxygen atom. Because of this reason, oxygen exists as a 2-atom molecule in its free state, thus attaining the molecular formula ${O_2}$.
Hence, whenever we represent oxygen as an element, we represent its most stable form, i.e. ${O_2}$.
Hence, one gram molecule of oxygen represents one mole of ${O_2}$

Hence, Option B is the correct option.

Note:
Oxygen also exists in a uni-atom molecule or tri-atom molecule structure. But these forms of oxygen are relatively less stable than ${O_2}$ and also their natural abundance is lower. Hence, these are not considered while writing the properties of oxygen as an element.