which best explains why ionization energy tends to decrease from the top to the bottom of a group? the…

Brief Explanations:

Ionization energy is the energy required to remove an electron from an atom. As we move down a group in the periodic table, the number of electron - shells increases. This causes the outermost electrons to be farther from the nucleus. The effective nuclear charge experienced by the outermost electrons decreases because of the shielding effect of inner - shell electrons. So, it becomes easier to remove an electron, and ionization energy decreases.

Answer:

Electrons get farther from the nucleus.