# How do polyatomic ions form compounds?

Jun 14, 2014

Poly atomic ions are covalent compounds that have an overall charge and therefore are held together through the electrostatic attraction of ionic bonding to positively charged ions called cations.

With the exception of ammonium, $N {H}_{4}^{+}$, these ions carry a negative

Examples include sulfate, $S {O}_{4}^{-} 2$, nitrate, $N {O}_{3}^{-}$, and phosphate, $P {O}_{4}^{-} 3$.

If we consider nitrate it will form one ionic bond with cation , such as sodium that has + one charge. The formula is $N a N {O}_{3}$

If nitrate bonds with calcium, two nitrate ions each with one calcium ion, $C a {\left(N {O}_{3}\right)}_{2}$

If nitrate bonds with aluminum which has a plus three charge, three nitrates are required to create an ionic compound, $A l {\left(N {O}_{3}\right)}_{3}$.