Question

A series of orbitals are given below. Identify the sets which represent the correct order of filling up of orbitals.
(A) $3s,3p,3d,4s,4p$
(B) $4s,4p,5s,4d,5p,4f$
(C) $2s,2p,3s,3p,4s,3d,4p$
(D) $1s,2s,2p,3s,3p,3d$

• A. A and B
• B. B and C
• C. B and D
• D. A and D

Answer 1

The correct option is B B and C

As per the Aufbau principle, the orbitals of lower energy are filled in first with the electrons and only then the orbitals of high energy are filled. The order of energy of orbitals are,

$1s<2s<2p<3s<3p<4s<3d<4p<5s<4d<5p<6s<4f<5d<6p<7s$

Hence, B and C represent the correct order of filling.