First thing, you need to know what this molecule is made of.
The First atom is the Strontium Sr (For more information, used usually as a substitute of the calcium in the human body).
The Second Atom is made of 2 Fluoride F2 (because it chemical name is Strontium difluoride).
Then, you join them together and Get [tex]SrF_2[/tex]
And for more information, Strontium fluoride is usually used as an optical material.
Hope this Helps :)