Question

which best explains why ionization energy tends to decrease from the top to the bottom of a group?
the number of orbitals decreases.
the number of neutrons decreases.
electrons get closer to the nucleus.
electrons get farther from the nucleus.

Explanation:

Ionization energy is the energy required to remove an electron from an atom. As we move from top to bottom in a group, 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, and it becomes easier to remove an electron, thus ionization energy decreases.

Answer:

Electrons get farther from the nucleus.