Question

Based on the actual electron configuration for $Cu$ provided in the previous question, how many core electrons and valence electrons does $Cu$ have?

• A. $18$ core electron and $11$ valence electrons
• B. $20$ core electron and $9$ valence electrons
• C. $27$ core electron and $2$ valence electrons
• D. $28$ core electron and $1$ valence electrons

Answer 1

Answer: (D)

$28$ core electron and $1$ valence electrons

The $4s$ subshell is valence shell and others are core shells. Thus for configuration $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{10}4s^1$ Cu has $2+2+6+2+6+10$ i.e., $28$ core electrons and $1$ valence electron hence answer is option D.