Chapter 8, Problem 8.52QP

Interpretation Introduction

Interpretation:

Aluminium has lower ionization energy than magnesium needs to be explained.

Concept Introduction:

• An atom can be converted into an ion by removing an electron from its outermost shell or adding electron to the outermost shell.  An amount of energy is required to remove an electron from the outermost shell of an atom to form a cation.  The minimum energy required for removing an electron from an atom in gaseous phase is known as ionization energy.
• If one electron is removed from the atom to form a cation, the energy required is known as first ionization energy.  If another electron is removed from the formed ion, the energy required is known as second ionization energy and this goes on.  Second ionization energy is higher than the first ionization energy because the effective nuclear charge increases.
• The trend followed in a periodic table for ionization energy is, it increases across the period and decreases down the group.  This is because; across the period, the electrons are added to the same orbital and hence decrease in shielding.  However, down the group, the electrons are added to a new sub-shell and hence increase in shielding.

To explain: why first ionization energy of aluminium is lesser than magnesium.