Electrons have a negative charge and are found outside the nucleus of an atom. The number of electrons is always the same as the number of protons and they can be found in everything from hydrogen to iron.
An arrangement of electrons around an atom's nucleus is sometimes called an electron cloud. Electrons are found in every type of atom although they are too small to be seen with an electron microscope. The atom with the smallest number of electrons is the hydrogen atom. It contains one electron and one proton. The uranium atom is the largest atom in existence, containing a total of 92 electrons.