An atom is the smallest building block of matter. Most of the atom is really just empty space but there are even smaller components as well. The three main parts of an atom are neutrons, electrons, and protons. The protons and neutrons are always in the center of the atom. This is called the nucleus. The electrons are negatively charged particles that move around the nucleus. Electrons are extremely small compared to the other parts of the atom. The mass of an electron is about 1000 times smaller than the mass of a proton. The proton has a positive charge and the neutron has a neutral charge.
Each atom is made up of certain particles called as subatomic particles. There are mainly three subatomic particles; electron, proton and neutron.