http://slideplayer.com/770516/2/images/8/The+ionization+energy+is+the+amount+of+energy+needed+to+strip+an+electron+off+of+an+atom+%2C+ion%2C+or+molecule.+The+illustration+shows+that+the+metals+like+lithium%2C+Li%2C+and+cesium%2C+Cs%2C+have+relatively+low+ionization+energies.+This+means+it+takes+relatively+small+amounts+of+energy+to+remove+electrons+from+these+atoms.+Metals+tend+to+lose+electrons+and+form+positive+ions..jpg