Question

What is the formula for the compound composed of calcium and phosphate?

Answer 1

A compound commonly refers to the end product of combining two or more individual elements together. These individual elements of fixed ratio need to be chemically bound together. These are called chemical compounds and are of two types – ionic compounds and covalent compounds.

Complete answer:
Calcium with the atomic number $20$, is represented by the chemical symbol $Ca$, is the fifth element and the third most common metal in the earth's crust. Calcium is a reactive alkaline earth metal. The calcium ion is a cation.
Phosphate is a salt and is a derivative of orthophosphoric acid. Orthophosphoric acid is composed of hydrogen ( $H$ ), oxygen ( $O$ ) and phosphorus ( $P$ ) and its chemical formula is ${H_3}P{O_4}$ . The phosphate ion is an anion.
When calcium hydroxide and orthophosphoric acid come together, their chemical reaction can be described by the following equation:
$Ca{(OH)_2} + {H_3}P{O_4} \to C{a_3}{(P{O_4})_2} + {H_2}O$
Here calcium cations ( $C{a^{2 + }}$ ) and phosphate anions ( $P{O_4}^{3 - }$ ) bond together to form calcium phosphate. The chemical formula of calcium phosphate is $C{a_3}{(P{O_4})_2}$ .
Calcium phosphate is a white compound and is found within the bones and teeth of many living organisms. It is also used in the production of fertilisers and has high nutrition value.

Note:
There are many compounds containing calcium and phosphate. They are broadly categorised into orthophosphates, di- and monohydrogen phosphates and di- and polyphosphates. The ratio of calcium cations ( $C{a^{2 + }}$ ) and phosphate anions ( $P{O_4}^{3 - }$ , ${H_2}P{O_4}^ -$ and/or $HP{O_4}^{2 - }$ ) determines the category of the calcium phosphate compound.