Question

How do you write the formula for zinc acetate?

Answer 1

Zinc acetate is an ionic compound. The easiest way to learn to write such a formula is to learn to write the formula of the cation first, and then the formula for the anion, then crisscross their charges.

Explanation:

The bond that forms zinc acetate is ionic. Zinc forms 2+ cations, with the formula `"Zn"^(2+)` and acetate is a polyatomic anion with the formula `"C"_2"H"_3"O"_2"^−`.

Since the compound needs to be neutral, the total positive charge must equal the total negative charge, so the formula for zinc acetate requires one `"Zn"^(2+)` and two `"C"_2"H"_3"O"_2"^−` ions.

The formula is then `"Zn"("C"_2"H"_3"O"_2)_2`. The formula for the acetate ion is placed in parentheses with a subscript of 2, indicating that two acetate ions with a 1- charge are required to bond with one zinc ion with a 2+ charge. Now the total positive charge is 2+ and the total negative charge is 2-, giving an overall charge of zero for the zinc acetate compound.

A very easy method for writing ionic formulas is called the crisscross method. It is shown in the diagram below.

Since a chemical formula for an ionic compound must indicate the lowest whole-number ratio of ions, sometimes after crisscrossing you must reduce the ratio.