Which of the following ions is known as nitrite?

Nitrite is represented by the chemical formula NO2-. This ion consists of one nitrogen atom and two oxygen atoms. Nitrites typically play a role in various chemical reactions and are often encountered in biological processes, especially in the nitrogen cycle, where they serve as intermediates in the conversion of ammonia to nitrates.

In contrast, the other options represent different ions. For instance, NO3- is nitrate, which has one nitrogen atom and three oxygen atoms, playing a different role in biogeochemical cycles. SO3 2- denotes the sulfite ion, which is involved in sulfur metabolism and has no relation to nitrogen compounds. HSO4- is the hydrogen sulfate ion, which is derived from sulfuric acid and serves different purposes in chemical reactions and does not pertain to nitrite.

Thus, the choice of NO2- as nitrite is accurate, aligning with its established chemical identity and functional role in various fields such as biochemistry and environmental science.