Question

Which of the following orbitals has most energy in multi-electron system?

• A. 4s
• B. 3s
• C. 4f
• D. 3d

Answer 1

The correct option is C

4f

This can be found out by Bohr - Bury's (n + l) rule

$For4s,n=4\&l=0\Rightarrow n+l=4$

$3s,n=3\&l=0\Rightarrow n+l=3$

$4f,n=4\&l=3\Rightarrow n+l=7$

$3d,n=3\&l=2\Rightarrow n+l=5$

Since (n + l) of 4f is most, it has most energy