Question

Which of the following quantum numbers are correct for the outermost electron of sodium atom?

• A. $n=4,l=0,m=0,s=\pm 1/2$
• B. $n=3,l=0,m=0,s=-1/2$
• C. $n=3,l=1,m=\pm 1,s=+1/2$
• D. $n=3,l=2,m=-1,s=-1/2$

Answer 1

Answer: (B)

$n=3,l=0,m=0,s=-1/2$

For sodium atom: atomic number = 11

thus its electronic configuration: $1s^{2}2s^{2}2p^{6}3s^1$

Outer most electron is in 3s orbital and has quantum numbers as:

$n=3,l=s=0,m_l=0,m_s=+1/2$ or $-1/2$