Question

The correct statements from the following are :
A. Ionic radii of trivalent cations of group 13 elements decreases down the group.
B. Electronegativity of group 13 elements decreases down the group.
C. Among the group 13 elements, Boron has highest first ionisation enthalpy.
D. The trichloride and triiodide of group 13 elements are covalent in nature.
Choose the correct answer from the options given below :

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

Hint:

Group 13 is full of anomalies! Always remember that Gallium is smaller than Aluminum in atomic radius due to the transition contraction, but the ionic radii follow a regular trend.

Answer 1

The Correct Option is A

To determine the correct statements among the given options, let's evaluate each statement based on the known properties of group 13 elements (B, Al, Ga, In, Tl):

1. Statement A: Ionic radii of trivalent cations of group 13 elements decrease down the group.
   • This statement is incorrect. As we go down the group, the ionic radii of trivalent cations actually increase due to the addition of extra electron shells, which outweighs the effective nuclear charge.
2. Statement B: Electronegativity of group 13 elements decreases down the group.
   • This statement is correct. Electronegativity generally decreases as we move down a group in the periodic table due to the increasing distance of the valence electrons from the nucleus and added electron shielding.
3. Statement C: Among the group 13 elements, Boron has the highest first ionisation enthalpy.
   • This statement is correct. Boron has the highest first ionisation enthalpy in group 13 because it has a relatively small atomic size and a relatively high effective nuclear charge that holds the electrons more tightly.
4. Statement D: The trichloride and triiodide of group 13 elements are covalent in nature.
   • This statement is correct. The trihalides of group 13 elements, such as trichlorides (e.g., BCl₃) and triiodides, form covalent bonds due to polarization effects and the sharing of electrons.

After evaluating each statement, the correct ones are C and D. Thus, the correct answer is:

C and D Only