4d, 5p, 5f and 6p orbitals are arranged in the order of decreasing energy. The correct option is :
- 6p > 5f > 4d > 5p
- 5f > 6p > 4d > 5p
- 5f > 6p > 5p > 4d
- 6p > 5f > 5p > 4d
Answer
(3) 5f > 6p > 5p > 4d
Solution
Use the (n + l) rule: higher (n + l) means higher energy; for equal (n + l), the orbital with higher n has higher energy.
4d: n + l = 4 + 2 = 6
5p: n + l = 5 + 1 = 6
5f: n + l = 5 + 3 = 8
6p: n + l = 6 + 1 = 7
∵ 4d and 5p both have (n + l) = 6, 5p (higher n) has higher energy than 4d.
∴ Decreasing energy: 5f > 6p > 5p > 4d
Answer: (3)