Question

Which one of the lanthanoids given below is the most stable in divalent form?

• A. Ce (Atomic Number 58)
• B. Sm (Atomic Number 62 )
• C. Eu (Atomic Number 63)
• D. Yb (Atomic Number 70)

Answer 1

Answer: (C)

Eu (Atomic Number 63)

Answer 2

The correct answer is (C) : Eu (Atomic Number 63)
Yb+2 is 4f14
Eu+2 is 4f7
but Eu+2 is more stable than Yb+2 because
$E°_{Eu|Eu^{2+}} > E°_{Yb|Yb^{2+}}$