Question on 1F.5 b

[Alvaro Chumpitaz 4D]

Which member of each pair is likely to have the smaller first ionization energy?
b) Mg or Na
The answer is Na but I do not necessarily understand why

[ckilkeary 2G]

The ionization energy is the energy it takes to remove an electron from an atom. Ionization energies are paired with atomic radius. Since atomic radius increases from left to right on the periodic table so does ionization energy. Na is to the left of Mg so this would mean that Na has the smaller atomic radius as well as the smaller first ionization energy.

[Joowon Seo 3A]

A good way to remember is that the farther away an electron is, the easier it is to remove. Since Na has a greater size than Mg, it is easier to remove an electron; therefore, Na has a lower ionization energy.

[Gabriella Bates 2L]

The ionization energy is the energy it takes to remove an electron from an atom. Ionization energies are paired with atomic radius. Since atomic radius increases from left to right on the periodic table so does ionization energy. Na is to the left of Mg so this would mean that Na has the smaller atomic radius as well as the smaller first ionization energy.

Actually, the atomic radius decreases from left to right, since the effective nuclear charge increases and the electrons are pulled more tightly towards the nucleus. This is why ionization energy increases across a group: electrons are pulled more strongly towards the nucleus, and are therefore more difficult to remove.