परमाणु

An atom is the smallest unit of a chemical element and the fundamental building block of all matter, consisting of a nucleus containing protons and neutrons surrounded by electrons held in place by electromagnetic forces. Atoms matter because the number of protons they contain determines what chemical element they are, and this atomic composition is what gives all materials their properties and determines how they behave and interact with one another.

AI-generated from the Wikipedia summary — may contain errors.