[tex]SrBr_{2}[/tex]
Chemical formulas are a way to show the elements and the amount of each element present in a compound.
Element Symbol
To write a chemical formula you need to use their chemical symbols. So, we need to find the symbols for strontium and bromide.
Charges
However, elements do not combine in random ratios. The ratios are based on charges so that all compounds have a neutral charge. Elements will have different subscripts to ensure that compounds have a neutral overall charge. So, to correctly write the formula we need to know the charges Sr and Br have when they became ions.
To cancel the positive 2 out, we must have 2 bromines. That means the final formula for strontium bromide is [tex]SrBr_{2}[/tex]. Now, the compound has a charge of 0.