Here's why:
* Sn represents the element tin.
* Cl represents the element chlorine.
* The subscript 2 indicates there are two chlorine atoms for every one tin atom.
* The Roman numeral II in the name indicates that tin has a +2 oxidation state in the compound.
Stannous chloride is the older, traditional name, while tin(II) chloride is the more modern and systematic name.
