Question

Arrange the following according to their ionization power 1) Li 2)Na 3)K

Answer 1

Ionisation power decreases down the group
Li<Na<K

Answer 2

Li>na>k
Ionisation potential is the energy required to remove an electron from an isolated gaseous atom. And as we go down a group no. Of shells increase so less energy is required to remove it. Thus ionisation potential decreases as we move down a group.
...hope it helps