What is ionization energy trend?

1 Answer
May 23, 2016

Ionization energies decrease down a Group but INCREASE across a Period, from left to right.


As a physical scientist you should seek out the data. As nuclear charge, #Z#, increases, the nucleus has greater electrostatic attraction for the valence electrons. The result is that (i) atomic radii decrease, and (ii) ionization enthalpies increase ACROSS the Period from left to right.

Down a Group, the valence electron is further removed from the nuclear charge, and inner electrons tend to shield #Z#. Ionization energies thus decrease.