Question

An atom of which of the following elements has the smallest first ionization energy?

Question options:

	Mg
	Sr
	Ca
	Ba
	Be0

Answer 1

The given elements belong to Group 2 of the periodic table. As we move down a group, the first ionization energy decreases. The ionization energy is defined as the energy required to remove the most loosely bound electron from the valence shell of an atom in its neutral gaseous state. As we move down the group, the atomic size increases and consequently, the electrons are held to the nucleus by weak forces of attraction. Therefore, it gets easier to remove the outer electrons and hence, the ionization energy decreases. Ba occurs at the bottom of Group 2 and will have the smallest first ionization energy.