Question

Be+ or Mg2+ which one has lower first ionisation enthalpy

Answer 1

Answer:

Be+ has higher ionisation energy as compared to Be.

Be+ has 3 e- in outermost which means electrons are strongly attracted towards the nucleus which in turn requires a lot of energy to remove the electron as compared to Be in which 4 e- are present . In this case electrons aren't that much strongly attracted towards the nucleus as in case of Be+ .. that's why ionisation energy of Be+ is always more than Be atom.

Alternate explanations :

We know that,

I.p. directly proportional to positive oxidation state of an atom . Ion with high positive Oxidation State will have higher ionization potential. E.g. Fe3+ > Fe2+ > Fe .