Question

Two electrons have the following sets of quantum numbers:
$X:n=3,l=2,m=-2,s=+\frac{1}{2}$
$Y:n=3,l=1,m=-1s=+\frac{1}{2}$
Which of the following is true?

• A. X and Y have same energy
• B. X has greater energy than Y
• C. X has less energy than Y
• D. X and Y represent same electron

Answer 1

The correct option is B X has greater energy than Y

From the given set of quantum numbers, electron X is in 3d and Y is in 3p.
According to Aufbau principle, higher energy will be of the orbital has higher value of $n+l$.
Since, $n+l$ value of 3d = 3 + 2 = 5
and $n+l$ value of 3p = 3 + 1 = 4
$\therefore$ X has greater energy than Y.