Question

What is the variation in ionisation enthalpy on moving from group-1 to group-2 in the periodic table?

Answer 1

The ionization energy is the energy required to remove a valence electron from its orbital around an atom to a point where it is no longer associated with that atom.

The ionization energy of an element increases as we move across a period in the periodic table because the electrons are held tightly by the higher effective nuclear charge.