# What do you know about a chemical compound by looking at its chemical formula?

So let's take a few formula, $N a C l$, $C {H}_{4}$, $F e S {O}_{4}$. All of these are real compounds; sodium chloride and ferrous sulfate are ionic, and methane is molecular. The formula does not tell you this, it gives you the chemical composition, and you have to know by experiment how it behaves.
$N a C l$, and $F e S {O}_{4}$ are binary salts of $N {a}^{+}$, $C {l}^{-}$, $F {e}^{2 +}$, and $S {O}_{4}^{2 -}$. The iron salts are a good example because we could also have $\text{ferric sulfate}$, i.e. $F {e}_{2} {\left(S {O}_{4}\right)}_{3}$, which gives $2 \times F {e}^{3 +}$, and $3 \times S {O}_{4}^{2 -}$.