Here's why:

* Iron (Fe): Iron can have different oxidation states, which are the positive or negative charges an atom can have. In this case, "ferrous" refers to the +2 oxidation state of iron.

* Chloride (Cl): Chloride is the anion (negatively charged ion) of chlorine. Chlorine has a -1 charge.

To balance the charges, we need two chloride ions (2 x -1 = -2) to balance the +2 charge of the ferrous iron.