An atom is made up of three particles including proton, neutron and electron. Neutron is a chargeless sub-atomic particle. The mass of a neutron is 1.6749 x 10-27 kg. Neutron does not effect the chemical properties of an element. Proton is a positive particle. Protons and neutrons are present in the nucleus of the atom. The charge on proton is positive 1.60217646 × 10-19 coulombs. The mass of a proton is 1.67262158 × 10-27 kilograms. Electron is negative sub-atomic particle. The charge of one electron is negative 1.60217646 × 10-19 coulombs. The mass of an electron is 9.10938188 × 10-31 kilograms. The mass of a proton and a neutron is same .The mass of negative particle of an atom is negligible as compared to the mass of proton and neutron. The chemical properties of an element depends upon the number of electrons present in an atom. Electrons move around the nucleus in the fixed orbits. Moreover, when electrons moves from one energy level to other energy levels, energy is released or absorbed by the electrons.