Question

Find out all quantum number for ${19}^{th}$ electron of Sc(Z=21).

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

Answer 1

Answer: (B)

$n=4,l=0,m=0,s=\frac{+1}{2}$

Sc (Z = 21)

Electronic Configuration : $\left[Ar\right]4s^{2}3d^1$

${19}^{th}$ electron is in 4s orbital

So, Quantum number for ${19}^{th}$ electron is

$n=4,l=0(s-orbital),m=0ands=+\frac{1}{2}$