Key Points: 1.What is Ionization Energy 2.Ionization Energy Examples 3.Ionization Energy Units 4.Is ionization Energy endothermic or exothermic reaction 5.Ionization Energy Trends Ionization Energy is defined as the minimum amount of energy required to remove the outermost electron from isolated, neutral gaseous atom . This will result in the formation of positively charged gaseous ionIonization Energy Trends – Chemistry Periodic Table – Digital Kemistry