Chapter 11, Problem 72A

(a)

Interpretation Introduction

Interpretation:

The most reactive non-metal needs to be determined.

Concept Introduction:

By accepting electrons, non -metals achieve a stable half-filled or full-filled configuration and these non-metals are most reactive in nature.

Answer to Problem 72A

Fluorine is the most reactive non-metal.

Explanation of Solution

The electronic configuration of fluorine is $1s^{2}2s^{2}2p^5$ . It is obvious from the electronic configuration of fluorine that it needs one electron to achieve noble gas neon configuration. Further, due to small size and high electronegativity, fluorine has a strong tendency to accept electrons from other elements.

(b)

Interpretation Introduction

Interpretation:

The smallest lanthanide element needs to be determined.

Concept Introduction:

The lanthanide contraction decreases more in ionic radii of the elements in the lanthanide series than expected.

Answer to Problem 72A

Lutetium is smallest lanthanide element.

Explanation of Solution

With an increase in the atomic number, nuclear charge increases. Shielding in a 4f sub-shell is lesser than in d sub-shell. As the nuclear charge increases, the valence shell is attracted slightly towards the nucleus. This causes lanthanide contraction.

Since the atomic number of lutetium is $71$ (highest in lanthanide), its size is the smallest.

(c)

Interpretation Introduction

Interpretation:

The largest metalloid in the periodic table needs to be determined.

Concept Introduction:

The metalloids are the elements which show the behavior of metals as well as non-metals.

Answer to Problem 72A

Polonium (Po) is the largest metalloid.

Explanation of Solution

As we move downwards, protons and electrons are being added to the same principal energy level. These electrons are gradually attracted closer to the nucleus. So, the radius of the atom decreases.

Since polonium is present in period 6 and group 16, its size is largest among metalloids.

(d)

Interpretation Introduction

Interpretation:

The metal with the lowest ionization energy has to be determined.

Concept Introduction:

Ionization energy is a measure of the difficulty in removing an electron from an atom or ion or the tendency of an atom or ion to lose an electron. This is the energy required. So, the process is endothermic.

Answer to Problem 72A

The element with the smallest ionization energy is cesium.

Explanation of Solution

Electronic configuration of cesium is $[Xe]6s^1$ . So, the removal of one electron from $6s$ orbital will give stable noble gas xenon configuration.

As we move downwards, the value of ionization energy decreases because the valence electrons are going away from the nucleus and feel more shielding and weak attraction Hence, Cesium has the lowest ionization energy.

(e)

Interpretation Introduction

Interpretation:

The least reactive halogen has to be determined.

Concept Introduction:

Halogens get less reactive as we go down the group.

Answer to Problem 72A

Astatine is the least reactive among the halogens.

Explanation of Solution

The electrons in the outer shell move away from the nucleus as we go down the group and the attractive pull between the electrons and the nucleus becomes less. So, the gain of an electron is not effective. Therefore, the reactivity of the atom reduces.

Since astatine is down the group in the halogen series it is least reactive.

(f)

Interpretation Introduction

Interpretation:

The least reactive member of the fifth period has to be determined.

Concept Introduction:

There are 10 transition metals in the fifth period

Answer to Problem 72A

Cadmium is the least reactive member of the fifth period.

Explanation of Solution

The electronic configuration of Cadmium is $[Kr]4d^{10}5s^2$ .

To react, an atom either gains or donates an electron. That is only possible if the valence electron shell is not filled completely.

If Cd undergoes reaction it has to break its highly stable full-filled outer electronic configuration.

(g)

Interpretation Introduction

Interpretation:

The actinide with the highest nuclear charge has to be determined.

Concept Introduction:

The nuclear charge is the charge an electron experiences in an atom with multiple other electrons present in the same atom.

In general $\text{nuclear charge}=\text{ number of protons}$

Answer to Problem 72A

Lawrencium has the highest nuclear charge.

Explanation of Solution

Actinides start from actinium $\text{(}Z=89)$ and end in lawrencium $\text{(}Z=103)$ .

Since lawrencium has the highest number of protons, its nuclear charge among the actinide is also highest.