What trends do you see on the periodic table for ionization energy and what causes these trends?

2 Answers
Oct 25, 2015


Ionization energy increases across a Period (from left to right); and decreases down a Group (top to bottom).


On simple electrostatic grounds, this is reasonable, as we go the right of the Periodic Table, the nuclear charge increases sequentially, and electrons are added to the same shell. Accordingly the Noble gases have the highest ionization energies inasmuch as they have the greatest nuclear charge. When we go down a Group, the valence shell of electrons moves farther away from the electropositive nucleus and nucleus-electron attraction should be minimized.

But don't take my word for it. You are a physical scientist. Get a list of ionization energies, and try to rationalize this on the basis of the Periodic Table. Good luck.

Nov 10, 2015


The further to the right and the higher you go, the higher the ionization energy.


Ionization energy is the energy required to remove one electron from an outer shell. This is mostly influenced by 2 factors:

  1. The larger the nucleus, the higher the ionization energy: This is because a larger Nucleus attracts electrons more.
  2. The farther away the electrons, and so, the more shells an atom has, the lower the ionization energy: This is because of the
    attraction the Nucleus has on the electrons. So, if an electron is farther away, it will require less energy to remove it, because it is less attracted to the nucleus.

You might still be asking why ionization energy trends go up and left, even though if you went down the mass of the nuclei would increase. This is because a change of one in the amount of shells is more noticeable than a change in one in the amount of Nuclear mass.

Hope it Helps! ;D .