Question

Which of the following has pseudo inert gas configuration?
a.) $N{{a}^{+}}$
b.) $C{{u}^{+}}$
c.) ${{K}^{+}}$
d.) ${{S}^{2-}}$

Answer 1

Hint: From inert gas configuration we can understand that octet should be complete. Here in this question we have to count the number of electrons in the outer shell of that atom or ion.

Step by step solution:
The electron configuration of an atom shows the placement of electrons around the atom's nucleus. The outermost electrons reside in what is known as the valence shell. The electrons in the valence shell are responsible for the sharing of electrons between atoms to form a bond.
The configuration of an ion of an element in which the shell with the highest energy level has 18 electrons instead of 8 electrons is called Pseudo inert gas configuration. Elements having d orbital also filled along with the s and p orbital are said to have pseudo gas configuration.
Inert gas atoms are chemically inert because they hold 8 valence electrons. The valence electron pattern in these atoms is called an inert gas electron configuration. Chemists also call this a Lewis octet. So, here we will see that configuration of each ion: $N{{a}^{+}}-1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}$
$C{{u}^{+}}-1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}3{{d}^{10}}$
${{K}^{+}}-1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}$
${{S}^{2-}}-1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{6}}$
Here, only $C{{u}^{+}}$ has 18 electrons in its outer shell. So, only $C{{u}^{+}}$has pseudo inert gas configuration and all others have inert gas configuration.
So, the correct answer is “B”.

Note: Here in this problem don’t get confused with inert gas configuration and pseudo inert gas configuration. In case of pseudo inert configuration there should be 18 electrons in the outermost shell.