What concepts describes the reason that atoms are larger and ionization energies are lower as you go down the periodic table?

1 Answer
Jan 5, 2018

Many factors influence these phenomena. However, a large factor is:

The effective nuclear charge of atoms dictates the Coulombic attraction strength regarding electrons and protons.

The way I was taught was the positive charge of the nucleus, although increasing, is increasingly "screened" as the equivalent number of core electrons screen the charge.

As a result, the valence electrons becomes increasingly diffuse, which increases the overall atomic radius and ease of ionization.

Here's an analogy my general chemistry text describes,

Chemistry the Central Science; Brown, et al.

As the level of "frost" (core electron screening) on the glass increases, the observer sees less and less light emission (the valence electrons experience less and less Coulombic attraction).