The compound of ammonium sulfate consists of two ions. NH4+ and SO42- both of which are polyatomic ions. a molecule of the compound consists of (one, two , or four) NH4+ ions and (one, two, or four) SO42- ions?

Blank #1: Polyatomic

Blank #2: 2 (see explanation)

Blank #3: 1 (see explanation)

Explanation

Both the ammonium ion  and the sulfate ion  contain more than one atom in each ion. The two species are thus polyatomic. The chloride ion , for example, is monoatomic.

Superscripts above formulae of the ions indicate their charge. Each ammonium ion carries a positive one (+1) charge. Each sulfate ion carries a charge of negative two (-2).

Ammonium sulfate is an ionic compound. A sample of this compound contain myriads of ammonium ions and sulfate ions. The ions are packed in three-dimensional lattices. Thus unlike water, ammonium sulfate does not exist as molecules in nature.

Assuming that the second and third blanks refers to a formula unit, rather than a molecule, of ammonium sulfate. The empirical formula of ammonium sulfate gives the minimum whole-number ratio between the two ions in a sample.

Charges shall balance between the two ions. Ammonium ions are of charge +1. Sulfate ions are of charge -2. The sample shall thus contain two ammonium ions for every one sulfate ion.

The empirical formula of ammonium sulfate is therefore .

There are thus two ammonium ions  and one sulfate ion  in each formula unit of ammonium sulfate.

astronomers such as edwin hubble.