Question

An ion has $18$ electrons in the outermost shell, it is

• A. $C{u}^{+}$
• B. $T{h}^{4+}$
• C. $C{s}^{+}$
• D. $K^{+}$

Answer 1

Answer: (A)

The electronic configuration of $Cu,Th,Cs$ and $K$ are
$Cu(29)=2,8,18,1$
$C{u}^{+}=2,8,18$
$Th(90)=2,8,18,32,18,10,2$
$T{h}^{4+}=2,8,18,32,18,8$
$Cs(55)=2,8,18,18,8,1$
$C{s}^{+}=2,8,18,18,8$
$K(19)=2,8,8,1$
$K^{+}=2,8,8$
Thus, $C{u}^{+}$has $18$ electrons in the outermost shell.