Answer to Question #158086 in General Chemistry for Teera

Question

• Explain how the ionization energy of atoms changes when proceeding down a group of the Periodic Table.

>generally decreases

>generally increases

>at first decreases and then increases

>at first increases and then decreases

• Explain why this change occurs.

>The nuclear charge is higher.

>The shielding of an atom's outermost electrons decreases.

>Electrons experience an increasingly stronger pull by the nucleus.

>Electrons are farther from the positively charged nucleus.

Answer 1

Ionization Energy is the quantity of energy (in kJ/mol) required to remove an electron from the outermost shell of a neutral or gaseous atom. Ionization energies are dependent upon the atomic radius of the atoms under consideration.

Since going down the group the atomic radius of the atoms increases, the ionization energies decreases. This is due to a decrease in the effective nuclear charge (the force of attraction between the positively charged nucleus and the negatively charged electrons) felt by the electrons in the outermost shell., as the atoms become larger.

In addition to increase in atomic radius down the group, there is also the effect of number of electrons between the nucleus and the electrons in the outermost shell (Shielding Effect), which increases down the group with increase in number of energy levels. The higher the shielding effect the lower the ionization energy.