4d, 5d, 5f and 6p orbitals are arranged in the order of decreasing energy. The correct option is : (1) 5f > 6p > 5p > 4d (2) 6p > 5f > 5p > 4d OR (2) 6p > 5f > 4d > 5p (4) 5f > 6p > 4d > 5p

Higher the sum of the Principal quantum number (n) and Azimuthal Quantum Number (l), higher the

energy of the orbital.

Energy of orbital is low for minimum (n+l). If, orbitals have same (n+1), then smaller the ‘n’, smaller

the energy..

(n + l) values for, 4d = 4 + 2 = 6

5p = 5 + 1 = 6

5f = 5 + 3 = 8

6p = 6 + 1 = 7

4d and 5p has same (n + l) value. Among them 4d has low ‘n’ and so, has lower energy than 5p.

6p will have lower energy than f, due to lower (n + l) value.

Decreasing order of energy of the given orbitals is 5f > 6p > 5p > 4d

Correct choice is (1)

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