Question

Cuprous ion is colourless, while cupric ion is colured because
A. both have unpaired electrons in the d-subshell
B. cuprous ion has a complete d-subshell and cupric ion has an incomplete d-subshell
C. both have half-filled p and d-subshell
D. cuprous ion has incomplete d-subshell and cupric ion has a complete d-subshell

Answer 1

Correct Answer - B
`Cu(Z=29):[Ar]^(18)4s^(1)3d^(10)`
`Cu^(2+)=[Ar]^(18)3d^(10)`
`Cu^(2+)=[Ar]^(18)3d^(9)`
`Cu^(+)` has completely filled d-subshell, while` Cu^(2+)` has incomplete d-subshell. As such `Cu^(+)` (cuprous) is colourless and`Cu^(2+)`(cupric) is blue.