Arrange the following elements in decreasing order of their radii:

(A) La
(B) Pr
(C) Gd
(D) Yb

Choose the correct answer from the options given below:

(A), (B), (C), (D)

The correct answer is Option (2) → (A), (B), (C), (D)

Arrange the elements in decreasing order of atomic radii: La, Pr, Gd, Yb.

Step 1: Consider periodic trends

• All these elements are lanthanides.
• Across the lanthanide series (La → Yb), the atomic/ionic radius decreases due to lanthanide contraction.

Step 2: Identify the order

• La (atomic number 57) → largest radius
• Pr (59) → slightly smaller than La
• Gd (64) → smaller than Pr
• Yb (70) → smallest

Step 3: Arrange in decreasing order

$\text{La} > \text{Pr} > \text{Gd} > \text{Yb}$