The formula Mg(NO₃)₂ represents magnesium nitrate. To determine the number of atoms, let's break it down:

* Mg: 1 magnesium atom

* (NO₃)₂: This represents two nitrate ions (NO₃)

* N: 2 nitrogen atoms (1 in each nitrate ion)

* O: 6 oxygen atoms (3 in each nitrate ion)

Therefore, there are a total of 9 atoms in one molecule of magnesium nitrate:

* 1 Magnesium atom

* 2 Nitrogen atoms

* 6 Oxygen atoms