Question

Consider the following elements In, Tl, Al, Pb, and Ge. The most stable oxidation states of elements with highest and lowest first ionisation enthalpies, respectively, are:

• A. +2 and +3
• B. +4 and +1
• C. +4 and +3
• D. +1 and +4

Hint:

Ionisation enthalpy trends in the periodic table influence the common oxidation states of elements, particularly for p-block elements where the inert pair effect is significant.

Answer 1

The Correct Option is B

Elements considered: Indium (In), Thallium (Tl), Aluminum (Al), Lead (Pb), Tin (Sn), Germanium (Ge).

Objective: Determine the most stable oxidation states for the elements exhibiting the highest and lowest first ionization enthalpies among the given set.

Periodic Table Positions:

• Aluminum (Al): Group 13, Period 3
• Germanium (Ge): Group 14, Period 4
• Tin (Sn): Group 14, Period 5
• Indium (In): Group 13, Period 5
• Lead (Pb): Group 14, Period 6
• Thallium (Tl): Group 13, Period 6

Ionization Enthalpy Trends:
- Ionization enthalpy generally increases across a period and decreases down a group.
- Within this group, Aluminum (Al) possesses the highest first ionization enthalpy due to its position as the uppermost and lightest element in its group.
- Thallium (Tl) exhibits the lowest first ionization enthalpy, attributed to its placement in Period 6, where the inert pair effect is pronounced.

Oxidation States Analysis:

Aluminum (Al), identified with the highest ionization enthalpy, typically displays a +3 oxidation state. This is its most stable oxidation state, reflecting the ease with which it loses its three valence electrons.

Thallium (Tl), characterized by the lowest ionization enthalpy, demonstrates both +3 and +1 oxidation states. However, the inert pair effect renders the +1 oxidation state more stable than the +3 state.

This stability trend is also observable in other heavier p-block elements such as Pb and Sn, where the +2 oxidation state becomes favored over the +4 state due to the inert pair effect.

Summary:
- The element with the highest first ionization enthalpy is Aluminum (Al), with a most stable oxidation state of +3.
- The element with the lowest first ionization enthalpy is Thallium (Tl), with a most stable oxidation state of +1.

Final Answer:
The final answer is $ (2)\ +4\ \text{and}\ +1 $.