In this video Emarald Robinson explains ‘what is an Atom?’ An atom is the smallest particle of an element that retains its properties. Atoms are the building blocks of everything existing in the universe. Atoms are in turn made up of even smaller particles called subatomic particles. The centre of an atom is called nucleus. Nucleus contains positively charged ‘Protons’ and electrically neutral ‘Neutrons’. The number of protons in an element determines an element’s physical properties. Negatively charged particles called ‘electrons’ revolve around the nucleus like planets revolve around the sun. Generally atoms have equal number of protons and electrons.