Question

What is the chemical formula of calcium phosphate?
A.${\text{Ca}}{\left( {{\text{P}}{{\text{O}}_4}} \right)_2}$
B.${\text{C}}{{\text{a}}_3}{\left( {{\text{P}}{{\text{O}}_4}} \right)_2}$
C.${\text{C}}{{\text{a}}_3}\left( {{\text{P}}{{\text{O}}_4}} \right)$
D.${\text{Ca}}\left( {{\text{P}}{{\text{O}}_4}} \right)$

Answer 1

In a compound, to maintain its neutrality the net cationic or positive charge must be equal to net negative or anionic charge in the species. However compounds failing to balance its charge have either a positive or negative charge depending upon the net charge on reacting species.

Complete step by step answer:
The chemical formula of calcium phosphate is ${\text{C}}{{\text{a}}_3}{\left( {{\text{P}}{{\text{O}}_4}} \right)_2}$ , as it is a salt with calcium ion as cation and phosphate ion as anion. The calcium carries $+ 2$ charge in its ionic form and on the other hand, the phosphate ion carries $- 3$ charge. In order to maintain neutrality of a compound; positive charge must be equal to negative charge. Otherwise, a salt cannot be neutral. Now in case of calcium carbonate, cation is calcium ion which carries $+ 2$ charge and anion is phosphate ion which carries $- 3$ charge, so to have a neutral salt of calcium phosphate three calcium ions must combine with two phosphate ions which corresponds to net charge zero. The total cationic or positive charge in calcium phosphate is $+ 6$ but it is neutralized by the total anionic or negative charge of phosphate ion $- 6$ .
We can also take an example of lime or calcium oxide which has the chemical formula of ${\text{CaO}}$ . As in this case, one calcium ion which tends to carry $+ 2$ charge combines with one oxygen ion which carries $- 2$ charge. The overall net charge on calcium oxide will be zero.

Thus, the correct option is B.

Note:
Oxidation state shows the total number of electrons which have been removed from an element with positive oxidation state or added to an element with a negative oxidation state to get its present state.