Question

The correct set of four quantum numbers for outermost electron of potassium ($Z=19$) is

• A. $4, 0, 0, \frac{1}{2}$
• B. $3, 1, 0, \frac{1}{2}$
• C. $4, 0, 0, \frac{1}{2}$
• D. $3, 0, 0, \frac{1}{2}$

Hint:

$s$-orbital $\rightarrow l=0, m=0$. Outermost shell for $K$ is $n=4$.

Answer 1

The Correct Option is C

Step 1: Configuration
Potassium ($Z=19$): $1s^{2}, 2s^{2}, 2p^{6}, 3s^{2}, 3p^{6}, 4s^{1}$.
Step 2: Valence Electron
The outermost (valence) electron is in the $4s$ orbital ($4s^{1}$).
Step 3: Quantum Numbers
- Principal ($n$) = 4
- Azimuthal ($l$) for $s$-orbital = 0
- Magnetic ($m_{l}$) = 0
- Spin ($s$) = $+1/2$ or $-1/2$.
Step 4: Conclusion
The correct set is $4, 0, 0, 1/2$.
Final Answer: (c)