Question

How many $d$-electrons in ${Cu}^{+}$ (Atomic number $=29$) can have the spin quantum number $(-\frac{1}{2})$?

• A. $3$
• B. $7$
• C. $5$
• D. $9$

Answer 1

Answer: (C)

$5$

The electronic configuration of $C{u}^{+}$ is $\left[Ar\right]3d^{10}$. It has ten d electrons. Out these, one half, i.e, 5 will have the spin quantum number $(-\frac{1}{2})$ and the remaining half will have the spin quantum number $(+\frac{1}{2})$.