# What is the chemical formula for cobalt (II) hydrogen carbonate?

Feb 10, 2017

The chemical formula for cobalt(II) hydrogen carbonate is "Co"("HCO"_3)_2.

#### Explanation:

The name tells you that this is an ionic compound, made of cobalt(II) ions and hydrogen carbonate ions.

The symbol for the cobalt(II) ion is $\text{Co"^"2+}$.

The symbol for the hydrogen carbonate ion is $\text{HCO"_3^"-}$ (you have memorized the formulas of the polyatomic ions, haven't you?).

So, the formula contains $\text{Co"^"2+", "HCO"_3^"-}$.

We need two "-" charges to balance the "2+" charges on the $\text{Co}$.

Thus, we need two hydrogen carbonate ions, so we enclose the formula in parentheses followed by a subscript 2.

The formula is "Co"("HCO"_3)_2