How many atoms of oxygen (O) are in one formula unit of Mg (NO3) 2?

The molecular formula indicates the number of atoms of each element in the molecule.

Oxygen exists as molecules (diatomic molecules). T he fundamental particles that make up a sample of Oxygen are pairs of atoms, rather than individual atoms.

You can count the number of atoms of each element in a chemical formula by multiplying the coefficient by the subscript, recognizing that those coefficients and subscripts that are not shown are equal to 1. So, in our case there are 6 atoms of oxygen.

We may use the molecular formula of the compound to determine the number of oxygen atoms in one formula unit. The formula unit is:

Mg (NO₃) ₂

Here, we can see that there are two nitrate ions in each mole, and each mole of nitrate ion contains three oxygen atoms. Thus, there are 6 oxygen atoms in each formula unit of magnesium nitrate.