Question

The radius of \( \text{La}^{3+} \) (Atomic number of La = 57) is 1.06 Å. Which one of the following given values will be closest to the radius of \( \text{Lu}^{3+} \) (Atomic number of Lu = 71)?

• A. 1.40 Å
• B. 1.06 Å
• C. 0.85 Å
• D. 1.60 Å

Hint:

Ionic radius tends to decrease as we move across a period due to increasing nuclear charge and constant shielding.

Answer 1

The Correct Option is C

Step 1: The ionic radius generally decreases across a period as the effective nuclear charge increases.
Step 2: Since \( \text{Lu}^{3+} \) is further across the periodic table than \( \text{La}^{3+} \), its radius is smaller. The closest value for the radius of \( \text{Lu}^{3+} \) is 0.85 Å.

Final Answer: \[ \boxed{0.85 \, \text{Å}} \]