What is the name of the compound (NH₄)₂SO₄? 

The name of the compound (NH₄)₂SO₄ is a ammonium sulphate. 

It is an ionic compound composed of two ammonium ions (NH₄+​)  and one sulfate ion (SO₄2−​). The ammonium ion is a positively charged polyatomic ion made up of one nitrogen atom bonded to four hydrogen atoms, carrying a +1 charge. On the other hand, the sulfate ion is a negatively charged polyatomic ion that consists of one sulfur atom surrounded by four oxygen atoms, carrying a 2− charge. To achieve electrical neutrality in the compound, two ammonium ions, each with a +1 charge, combine with one sulfate ion, which has a 2− charge.

This compound is widely used in agriculture as a fertilizer because it provides two essential nutrients: nitrogen, which supports plant growth, and sulfur, which improves crop quality. Apart from its use in fertilizers, ammonium sulfate is also utilized in water purification processes and in certain industrial applications, such as flame retardants and protein purification in biochemistry. The systematic naming of the compound reflects its ionic components, with "ammonium" referring to the cation and "sulfate" to the anion.