Question

How ionisation energy vary about the group in a periodic table?

Answer 1

Ionisation potential decrases as one moves down a group.
There is an increase in the atomic number and atomic size down the group due to the addition of extra shells. This increase in in the atomic size overcomes the effect of an increase in the nuclear charge.
therefore, ionisation energy decreases with increase in the atomic size, i.e., it decreases as one moves down a group


with regards...

Answer 2

Moving left to right within a period or upward within a group, the first ionization energy generally increases. As the atomic radius decreases, it becomes harder to remove an electron that is closer to a more positively charged nucleus.