Question

Which of the following order(s) is/are correct regarding the property indicated?

• A. B > TI > Ga > Al > In (First ionisation enthalpy)
• B. B > TI > In > Ga > Al(Electronegativity)
• C. TI > In > Al > Ga (Metallic radius)
• D. B > Al > Ga > In > TI (Melting point)

Answer 1

Answer: (A), (C)

Options A and C.

Answer 2

Solution:

1. First Ionisation Enthalpy for B, Tl, Ga, Al, In:

   Known values (in kJ/mol):

   • B ≈ 800.6
   • Tl ≈ 589.4
   • Ga ≈ 578.8
   • Al ≈ 577.5
   • In ≈ 558.3

   Order: B > Tl > Ga > Al > In.

   Thus, Option A is correct.

2. Electronegativity for B, Tl, In, Ga, Al:

   Pauling EN values (approx.):

   • B ≈ 2.04
   • Ga ≈ 1.81
   • In ≈ 1.78
   • Tl ≈ 1.62
   • Al ≈ 1.61

   Correct descending order should be: B > Ga > In > Tl ≈ Al.

   Option B is not correct.

3. Metallic Radius for Tl, In, Al, Ga:

   Metallic radius increases downward:

   Approximate trend: Ga < Al < In < Tl

   Thus order: Tl > In > Al > Ga.

   Option C is correct.

4. Melting Point for B, Al, Ga, In, Tl:

   Melting points (approx.):

   • B ≈ 2349°C
   • Al ≈ 660°C
   • Tl ≈ 304°C
   • In ≈ 156°C
   • Ga ≈ 30°C

   Correct descending order: B > Al > Tl > In > Ga.

   Option D is not correct.

Core explanation:

Using known numerical data: Option A’s ordering for first ionisation enthalpy (B > Tl > Ga > Al > In) and Option C’s ordering for metallic radius (Tl > In > Al > Ga) match the trends. The other orderings don’t match the correct trends.