What is the correct formula for calcium phosphate?

##"Ca"_3("PO"_4)_2##

Calcium phosphate is composed of three calcium cations, ##"Ca"^(2+)##, and two phosphate anions, ##"PO"_4^(3-)##. The chemical formula for this compound is

##["Ca"^(2+)]_3["PO"_4^(3-)]_2 <=> "Ca"_3("PO"_4)_2##

-- Hint: 1. Familiar yourselves with the odixation numbers of elements or ions. Oxidation numbers are the superscripts (either + or -) you find at the right portion of the element or ions. 2. When writing the compound: the metal element always comes first (indicated by the + superscript/ oxidation number), followed by the ion (- superscript/ oxidation number). Signs for oxidation should always be opposite, never alike! 3. "Cross multiply" the superscripts of both element and ion, making it the subscript of the other. Vice versa. 4. If both superscripts are numerically the same, i.e. 2+ and 2-, cancel them out. They are automatically equal to 1.