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

Hint: In this question, we need to find out which of the four configurations has $18$ elements in its outermost shell. Firstly, we will write down the electronic configuration of all the four given configurations and then identify which of them has $18$ electrons in the outermost shell. There are a number of configurations with $18$ electrons in its outermost shell but we need to identify the one present in the given four options.

Complete Step by Step Solution:
The electronic configuration is also called an electronic structure. It is the arrangement of electrons in different energy levels around the atomic nucleus. According to the atomic model, electrons occupy several levels starting from the first level nearest to the nucleus which is the K shell.

The electronic configuration of $Cu(29)$is $2,8,18,1$
The electronic configuration of $Th(90)$is $2,8,18,32,18,10,2$
The electronic configuration of $Cs(55)$is $2,8,18,8,1$
The electronic configuration of $K(19)$is $2,8,8,1$
The E.C (Electronic configurations) of the given ions are:
$C{u^ + }(28) = 2,8,18$
$T{h^{4 + }}(86) = 2,8,18,32,18,8$
$C{s^ + }(54) = 2,8,18,8$
${K^ + }(18) = 2,8,8$
Thus, $C{u^ + }$has 18 electrons in its outermost shell.
Hence, the correct option is (A).

Note: This question is taken from the inorganic part of Chemistry. This branch of chemistry is concerned with the properties and behaviour of inorganic compounds, which include metals, minerals, and other organometallic compounds.