Atom is the primary as well as smallest unit of element.
Atoms are the tiny blocks that build elements. They are composed of proton, electron, and neutron. The electron is negatively charged, protons are positively charged, and neutrons are devoid of any charge.
The atom present in the elements combine with one another and leads to the formation of molecules. The property of the atom remains unchanged even after involved in formation of new molecules. When two atoms combine together it is called as molecules.