Atom

An atom is the smallest unit of matter. The smallest atom is the hydrogen atom that in its neutral state consists of just one proton with an electron orbiting or creating a field round it. All elements heavier than hydrogen include at least one neutron (deuterium) or neutrons for anything heavier. Elements heavier than the different types of hydrogen include more protons and roughly equal numbers of neutrons. The number of protons in an atom determines which chemical element it is. In their neutral state the number of electrons is exactly equal to the number of protons. Protons carry a positive charge which exactly balances the negative charge in the electron, therefore atoms with equal numbers of protons and electrons are electrically neutral. Sometimes especially when atoms are heated they can lose one or more of their electrons, then they are no longer electrically neutral, the free electrons are positively charged and the nuclei are negatively charged. Both respond to magnetic fields in their area.