Electrons – The lightest subatomic particle is the electron at 9.11×1031 kg. It is almost massless in comparison to protons and neutrons and behaves like both a wave and a particle. The electron is one of the lightest subatomic particles and one of the key components of atoms, along with neutrons and protons.
The electron was the first subatomic particle discovered. It was identified in 1897 by the British physicist J.J. Thomson during investigations of cathode rays. The discovery of electrons as the ultimate carriers of electricity not only established the materialistic origin of electricity but also opened up a whole new vista for our microscopic understanding of the flow of electricity. Not all electrons are associated with atoms. Some occur in a free state with ions in the form of matter known as plasma.
The number of electrons in an atom is equal to the number of protons and this is called the atomic number Z. The atomic number is the number of protons in the atom. Each element has its own unique atomic properties. Electrons have an electric charge of -1, which is equal but opposite to the charge of a proton, which is +1