Quantum is the smallest quantity of energy that can be emitted (or absorbed) in the form of electromagnetic radiation. Energy of a quantum (E) is equal to
E = h·ν
where h is Planck constant and ν is the frequency of radiation.
Citing this page:
Generalic, Eni. "Quantum." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.