Question

An ion has 18 electrons in the outermost shell it is
A. `Cu^(+)`
B. `Th^(4+)`
C. `Cs^(+)`
D. `K^(+)`

Answer 1

Correct Answer - A
(a) The electronic configuration of Cu, Th, Cs and K are
Cu(29) = 2, 8,, 18, 1
`Cu^(+) = 2,8,18`
Th(90)= 2, 8, 18, 32, 18, 10, 2
`Th^(4+)=2, 8, 18, 32, 18, 8
Cs(55) = 2, 8, 18, 18, 8,1
`Cs^(+)=2, 8, 18, 18, 8`
K(19)=2, 8, 8, 1
`K^(+)=2, 8, 8`
Thus, `Cu^(+)` has 18 electrons in the outermost shell.