Particles with charges, also known as ions, are atoms or molecules that have either gained or lost electrons, resulting in a net positive or negative charge. Ions are formed when an atom or molecule gains or loses electrons, which can be caused by chemical reactions, such as the transfer of electrons between two atoms. Ions are important in many biological processes, such as muscle contraction and nerve impulse transmission. They are also essential for the formation of salts, which are used in many industrial processes.