An ion that has 18 electrons in the outermost shell is

Options

A. `cu^(+)`
B. `Th^(4+)`
C. `Cs^(+)`
D. `K^(+)`

Answer

A

Explanation

Atomic number of Cu=29
Electronic configuration of Cu is `1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(10)4s^(1)`
Electronic configuration of `Cu^(+)" is "1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)3d^(10)`
Thus, outermost shell contains 18 electrons.