Question

Question #734cf

Answer 1

Ammonium sulfate, `(NH_4)_2SO_4`, is not purely covalent because the compound is held together by an ionic bond formed between a cation and an anion.

More specifically, ammonium sulfate is composed of two ammonium cations, `NH_4^(+)`, and one sulfate anion, `SO_4""^(-)`.

Both of these polyatomic ions are covalent compounds, i.e. the atoms that form the polyatomic ion are all covalentrly bonded, but they are able to form ammonium sulfate because of the electrostatic attraction that exists between the positive charge on the cation and the negative charge on the anion.

As a result, these two polyatomic ions will he held together by an ionic bond. Notice that because the sulfate anion has a charge of 2-, you need +1 two ammonium ions to balance it out.

Read more on polyatomic ions and ionic bonding here:

http://socratic.org/questions/how-do-polyatomic-ions-bond