# Question #c8ac6

Jun 14, 2015

Only two of the compounds listed are actually ionic.

#### Explanation:

Phosphoric acid, ${H}_{3} P {O}_{4}$, is predominatly a covalent compound, so you can't say that it is made up of ions. All the bonds in phosphoric acid are polar covalent, so you can't label it as being ionic.

Silver chromate, $A {g}_{2} C r {O}_{4}$, is indeed a predominatly ionic compound formed when two silver cations, $A {g}^{+}$, are ionically bonded to one chromate anion, $C r {O}_{4}^{2 -}$, which is a polyatomic ion.

Since the chromate ion has a 2- charge, you need two 1+ silver ions to make a neutral compound.

Silver chromate thus contains two types of ions

• Positively charged ions: $A {g}^{+}$
• Negatively charged ions $C r {O}_{4}^{2 -}$

The first compound you listed should actually be $B {e}_{3} {\left(P {O}_{4}\right)}_{2}$, beryllium phosphate, not $B {e}_{3} {\left(P {O}_{4}\right)}_{3}$,

Beryllium is located in period 2, group 2 of the periodic table, so it can lose two electrons from its outermost shell to form the beryllium cation, $B {e}^{2 +}$.

The phosphate polyatomic ion, $P {O}_{4}^{3 -}$, has a 3- charge. This means that, in order to get a neutral compound, you need 3 beryllium cations and 2 phosphate anions.

Thus, beryllium phosphate contains

• Positively charged ions: $B {e}^{2 +}$
• Negatively charged ions: $P {O}_{4}^{3 -}$