Which of the following elements has the smallest first ionization energy?Group of answer choicesAsFMgIRb

The element with the smallest first ionization energy among As, F, Mg, I, and Rb is Rb (Rubidium).

Here's why:

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The first ionization energy refers to the energy to remove the first electron from a single atom.

The ionization energy generally increases from left to right across an element period (row) in the periodic table. This is because the electrons are held tighter by the higher effective nuclear charge.

On the other hand, the ionization energy decreases from top to bottom in a group (column) in the periodic table. This is because the outermost electrons are further from the nucleus and thus are not held as tightly by the atom.

In the given list, Rubidium (Rb) is the furthest down the periodic table (Period 5, Group 1), which means it has the lowest first ionization energy.