Question

The correct set of four quantum number values for the valence electron of sodium atom is

• A. n=3,l=1,m=1,s=-\(\frac{1}{2}\)
• B. n=3,l=0,m=0,s=+\(\frac{1}{2}\)
• C. n=3,l=0,m=1,s=+\(\frac{1}{2}\)
• D. n=3,l=1,m=0,s=-\(\frac{1}{2}\)

Answer 1

The Correct Option is B

To solve this question, we need to find the correct quantum numbers for the valence electron of a sodium atom.

1. Electronic Configuration of Sodium (Na):
Atomic number of sodium = 11
Electronic configuration = 1s² 2s² 2p⁶ 3s¹
So, the valence electron is in the 3s orbital.

2. Quantum Numbers: For the 3s¹ electron:

• Principal quantum number \( n = 3 \) (third shell)
• Azimuthal quantum number \( l = 0 \) (s orbital)
• Magnetic quantum number \( m = 0 \) (only one value for s orbital)
• Spin quantum number \( s = +\frac{1}{2} \) (can be either +½ or -½, usually +½ is taken)

3. Evaluating the Options:

• (1) \( n = 3, l = 1 \) – Incorrect; l = 1 corresponds to p-orbital
• (2) \( n = 3, l = 0, m = 0, s = +\frac{1}{2} \) – Correct ✔
• (3) \( n = 3, l = 0, m = 1 \) – Incorrect; m must be 0 for l = 0
• (4) \( n = 3, l = 1 \) – Incorrect; same reason as (1)

Final Answer:
The correct answer is (B) \( n = 3, l = 0, m = 0, s = +\frac{1}{2} \).