Mass of ${{O}_{2}}$ molecule is:

Hint: The answer to this question is based on the basic concepts that includes the periodic table where the information of atomic mass of one oxygen atom is given that is 16 g/mol and then calculating the value for one molecule of oxygen.

Complete step by step answer:
We have studied the periodic table that plays an important role in chemistry that tells us about the elements and their properties too.
Now we shall see what the periodic table is and how can we calculate the mass of one molecule of oxygen.
- Periodic table is the orderly arrangement of atoms existing in nature that is arranged according to their increasing atomic number assigned in terms of groups and period.
- It gives the information about the atomic mass of a single atom in it. Thus, based on this periodic table, the atomic mass of one oxygen atom is 16.00 amu.
- Since oxygen always exist as diatomic, the total mass of two oxygen atoms which makes it a molar mass will be,
$2\times 16.00=32.00g/mol$
- Therefore, the mass of one mole of oxygen atom will be 32 g/mol.
To calculate the mass of oxygen molecule, we have to multiply the above value with the Avogadro number of molecules that is $6.023\times {{10}^{23}}$
Therefore, the mass of one molecule of oxygen will be,
$\dfrac{32.00}{6.023\times {{10}^{23}}}=5.31\times {{10}^{-23}}g$

Thus, the mass of one molecule of ${{O}_{2}}$ is $5.31\times {{10}^{-23}}g$.

Note: Do not be confused about the molecular mass and mass of one molecule where the molecular mass is the mass of Avogadro number of molecules and mass of a molecule is the mass of a single molecule which is also its actual mass. The molecular mass of${{O}_{2}}$ in an atomic mass unit is $32 amu$.