Question

How many electrons in copper atom $(_{29}Cu)$ have $(n + l) = 4$

• A. 6
• B. 7
• C. 8
• D. 4

Answer 1

Answer: (B)

7

Answer 2

$_{29}CU$ is $1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1$. The electrons having $(n + l) = 4$ are present in $3p$ and $4s$ shells. Hence total number of such electrons is $7$.