Which of the following acts as a strong reducing agent? (Atomic number: Ce = 58, Eu = 63, Gd = 64, Lu = 71)
- Eu2+
- Gd3+
- Lu3+
- Ce4+
Answer
(1) Eu2+
Solution
Common (most stable) oxidation state of lanthanoids = +3.
(1): Eu2+ (4f7) Eu3+ (4f6) + e- ⇒ (1) is a strong reducing agent
(2): Gd3+ (4f7, half-filled) ⇒ (2) is stable, not reducing
(3): Lu3+ ( 4f14, full) ⇒ (3) is stable, not reducing
(4): Ce4+ + e- Ce3+ ⇒ (4) is an oxidising agent
∵ As per NCERT, Eu2+ is a strong reducing agent, changing to the common +3 state.
Answer: (1)