Here's how to understand the formula:

* Calcium (Ca): The symbol for calcium, a Group 2 element.

* Ethanoate (CH₃COO⁻): The anion formed from ethanoic acid (acetic acid), which has the formula CH₃COOH. The ethanoate ion loses a hydrogen ion (H⁺) to become CH₃COO⁻.

Note: Calcium has a +2 charge (Ca²⁺), while ethanoate has a -1 charge (CH₃COO⁻). To balance the charges, we need two ethanoate ions for every calcium ion.