Question

The quantum numbers of most energetic electron in Ar atom when it is in first excited state is:

• A. $2,1,0,\pm \frac{1}{2}$
• B. $4,1,1,\pm \frac{1}{2}$
• C. $4,0,0,\pm \frac{1}{2}$
• D. $4,1,0,\pm \frac{1}{2}$.

Answer 1

The correct option is C $4,0,0,\pm \frac{1}{2}$

The electronic configuration of Ar atom is $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$.

In the first excitation state, the electron from 3p will unpair and shift to 4s where its quantum numbers will be $4,0,0,\pm \frac{1}{2}$.