Compare the first ionization energy of sodium to that of potassium

Sodium is higher than Potassium in thesame group

Explanation:

Sodium and potassium are the elements present in the first group of the periodic table. In group, atomic size increases from top to bottom this implies that even atomic radius increases. This causes less attraction force by nucleus on the electrons of outermost orbit of the atom and hence reduces the first ionisation energy, which is the energy required to remove the electron from the outermost orbit of an atom. So, as potassium is below sodium in the group, sodium has greater ionisation energy than potassium