Ionization Energy
The amount of energy required for the complete removal of 1 mol
of electrons from 1 mol of gaseous atoms or ions; an energy-
requiring process; value is positive in sign
IE1 = first ionization energy: removes an outermost electron from
the gaseous atom: atom(g) ion+(g) + e- ČE = IE1 > 0
IE2 = second ionization energy: removes a second electron from the
gaseous ion: ion+(g) ion+2(g) + e- ČE = IE2 > IE1
Atoms with a low IE1 tend to form cations during reactions, whereas those
with a high IE1 (except noble gases) often form anions.
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