All matter is composed of one or more atoms. Each __________________ is composed of ___________________ with a unique number and arrangement of subatomic particles. These subatomic particles include protons, neutrons, and electrons. Together, positively charged ______________________ and uncharged ___________________ make up the nucleus of an atom. Negatively charged electrons orbit the nucleus in _________________________. When an atom gains or loses an electron, an electrically charged ____________________ is formed. Atoms with additional neutrons are called