Chapter 9, Problem 121A

(a)

Interpretation Introduction

Interpretation: To arrange the given groups of elements in the increasing order of their ionization energy.

Concept Introduction: Ionization energy is the energy that must be provided to an isolated gaseous atom to remove its most loosely bound electrons. It is expressed in electron volts or joules.

Answer to Problem 121A

The increasing order of ionization energy of the given elements is:

Cesium < potassium < sodium < lithium.

Explanation of Solution

The value of ionization energy of elements decreases while moving down the group in the periodic table. The given elements belong to the first group and their size increases on moving down the group hence ionization energies vary as shown above.

(b)

Interpretation Introduction

Interpretation: To arrange the given groups of elements in the increasing order of their ionization energy.

Concept Introduction: Ionization energy is the energy that must be provided to an isolated gaseous atom to remove its most loosely bound electrons. It is expressed in electron volts or in joules. Ionization energy increases on moving from left to right along a period.

Answer to Problem 121A

The ionization energies of the given elements increase in the order:

Lithium < boron < carbon < fluorine < neon

Explanation of Solution

Ionization energy increases on moving from left to right across a period in the periodic table. As we move from left to right across a period, the atomic size of elements decreases whereas the nuclear charge increases, thus ionization energy increases. So, neon being at the right end of the second period has the highest ionization energy than the rest of the second-period elements.