What is the correct electron configuration of the ${\text{C}}{{\text{u}}^ + }$ ion?

A.     ${\text{[Ar] 3}}{{\text{d}}^{\text{9}}}{\text{ 4}}{{\text{s}}^{\text{1}}}$

B.     ${\text{[Ar] 3}}{{\text{d}}^{\text{7}}}{\text{ 4}}{{\text{s}}^{\text{2}}}$

C.     ${\text{[Ar] 3}}{{\text{d}}^{{\text{10}}}}$

D.     ${\text{[Ar] 3}}{{\text{d}}^{\text{8}}}{\text{ 4}}{{\text{s}}^{\text{1}}}$

C

One respondent stated that the question should not have been asked, as students are not supposed to know the Cu exception. In the teacher’s notes of assessment statement 12.1.6 in the syllabus details it is clearly stated “exceptions to the principle for copper and chromium should be known”. 56.49% of the candidates chose the correct answer C, with 30.78% choosing A which means that about one-third of the schools do not teach these two exceptions.