An ion is an atom which has lost or gained one or more electrons so that it has a net electrical charge. Normally atoms have equal numbers of negatively charged electrons and positively charged protons so that the total charge of the atom is zero
Space Science Institute (SSI),Space Weather Center, Glossary of Space Weather-Related Terms, Colorado, USA 2011. http://www.spaceweathercenter.org/glossary/001/01. html, (Space Wthr - Amer) {860}