ion EnthalpyIonization Enthalpy of ELEMENTS is the amount of energy that an isolated gaseous atom requires to LOSE an electron in its ground state. Losing of electrons results in the formation of cations.The first IONIZATION energy of element A is the energy required by an atom to form A+ IONS.  The unit of ionization energy is given as KJ mol-1.A (g) → A+ (g) + e–An element's metallic properties refer to its propensity to behave like the elements that are classified as metals in the periodic table.This depends on the set of chemical properties commonly associated with the metallic elements, specifically the ability of an element to lose its outer valence electrons.The metallic character of an element depends on how readily it can lose its electrons. This results in the element exhibiting chemical properties like the ability to be reduced, the ability to form ionic chlorides and basic oxides and the ability to displace hydrogen from dilute acids. Metallic character decreases from left to right and increases from top to BOTTOM on the periodic table.