What Is Atom?

An atom is the basic unit of an element. An atom consists of three sub-atomic particles. These sub-atomic particles are electrons, protons and neutrons. The neutrons are chargeless particles. Proton has positive charge and electron has negative charge. Nucleus is the positive part of the atom. A nucleus consists of protons and neutrons. The electrons revolve around the nucleus. The whole mass of an atom is present at the centre of the atom or based upon the mass of nucleus. Moreover, when an atom loses or gains electrons, positive and negative ions are formed.