Here's a breakdown:

* C₄: Indicates there are four carbon atoms in the ion.

* H₄: Indicates there are four hydrogen atoms in the ion.

* O₆: Indicates there are six oxygen atoms in the ion.

* ²⁻: Indicates that the ion has a charge of -2.

This is the general formula for the tartrate ion. There are two possible stereoisomers, but the formula remains the same.