Question

The electronegativity of a group 13 element 'E' is same as that of Ge (on Pauling scale and upto one decimal point). The CORRECT statements about \( E^{3+} \) are:
A. It can act as a reducing agent.
B. It can act as an oxidizing agent.
C. \( E^{3+} \) is more stable than \( E^+ \).
D. The standard electrode potential value for \( E^{3+}/E \) is positive.
Choose the correct answer from the options given below:

• A. A and C Only
• B. B and C Only
• C. B and D Only
• D. A and D Only

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Identify the element 'E' based on its group and electronegativity. Once 'E' is identified as Thallium (Tl) due to periodic trends, apply the concept of the Inert Pair Effect to determine the stability of its oxidation states and its resulting redox behavior.
Step 2: Key Formula or Approach:
Electronegativity trend in Group 13: B(2.0), Al(1.5), Ga(1.6), In(1.7), Tl(1.8).
Electronegativity of Ge = 1.8.
Inert Pair Effect stabilizes the lower oxidation state ($+1$) relative to the higher oxidation state ($+3$) in heavy post-transition metals like Tl.
Step 3: Detailed Explanation:
The group 13 element with an electronegativity of 1.8 (equal to Ge) is Thallium (Tl).
Let's evaluate the properties of Thallium ($E = \text{Tl}$):
Because Tl is at the very bottom of Group 13, its outermost s-electrons ($6s^2$) are strongly attracted to the nucleus due to poor shielding by internal d and f orbitals. This is known as the Inert Pair Effect.
Consequently, for Thallium, the $+1$ oxidation state is significantly more stable than the $+3$ oxidation state.
Let's check the given statements:
C. False. Tl$^{3+}$ is much less stable than Tl$^+$.
A. False. A reducing agent forces reduction by being oxidized itself. Tl$^{3+}$ is already at its maximum group oxidation state and cannot be oxidized further.
B. True. Since Tl$^+$ is much more stable than Tl$^{3+}$, Tl$^{3+}$ strongly desires to gain two electrons to reduce down to Tl$^+$. Therefore, it acts as a strong oxidizing agent.
D. True. Because Tl$^{3+}$ is highly eager to undergo reduction, the standard reduction potential $E^\circ$ for Tl$^{3+} + 3e^- \to \text{Tl}$ (and also Tl$^{3+} \to$ Tl$^+$) is a highly positive value, indicating a spontaneous reduction process.
Thus, statements B and D are correct.
Step 4: Final Answer:
Options B and D Only are correct.