Question

The following sets of quantum numbers represent four electrons in an atom.
(i) $n=4,l=1$ (ii) $n=4,l=0$
(iii) $n=3,l=2$ (iv) $n=3,l=1$
The sequence representing increasing order of energy, is

• A. (iii) < (i) < (iv) < (ii)
• B. (iv) < (ii) < (iii) < (i)
• C. (i) < (iii) < (ii) < (iv)
• D. (ii) < (iv) < (i) < (iii)

Answer 1

Answer: (B)

(i) 4 p (ii) 4 s
(iii) 3 d (iv) 3 p
According to Bohr Bury's (n + $\ell$) rule, increasing order of energy will be (iv) < (ii) < (iii) < (i).
Note : If the two orbitals have same value Of (n | $\ell$) then the orbital with lower value of n will be filled first.