# Question #7639c

$M g C {l}_{2}$ originated from Magnesium (Mg) and Chlorine (Cl) atoms.
There is one Mg atom and two Cl atoms (since there is a 2 after the Cl) that forms the compound $M g C {l}_{2}$.
It works that way because $M g C {l}_{2}$ is made up of positive $M {g}^{2} +$ ions and negative $C {l}^{-}$ ions. In order for $M {g}^{2} +$ and $C {l}^{-}$ to bond together, the 2 from $M {g}^{2} +$ moves to the end of Cl so that makes $M g C {l}_{2}$.
Therefore, $M g C {l}_{2}$ contains $M g$ and $C l$ elements and there are 3 atoms altogether.