Which of these is true of the first ionization energy within a group?

Question 13 options:

There is no pattern of ionization energy within a group.

The first ionization energy does not vary within a group.

The first ionization energy increases from top to bottom within a group.

The first ionization energy decreases from top to bottom within a group.

As you move down a group, first ionization energy decreases. Electrons are further from the nucleus and thus easier to remove the outermost one

The correct option is: "The first ionization energy decreases from top to bottom within a group."

Explanation:

The electrons are attracted to the nucleus and it is necessary to provide energy to start them. Then the ionization energy, I, is the energy necessary to pull an electron from a gaseous atom, isolated and in a fundamental state. Generally the outermost electron is removed, which is more weakly retained.

This can be expressed as:

A (g) + IE → A⁺ (g) + e⁻

As you go down the periodic table in a group, the atoms increase in size, with the electrons less and less attracted to the nucleus. This facilitates its extraction from the atom and less energy is required. Then by going down in a group the ionization energy decreases.

The correct option is: "The first ionization energy decreases from top to bottom within a group."