Question

Which of the following pairs of compounds is isoelectronic and isostructural?
A. $I{F_3},\,Xe{F_2}$
B. $BeC{l_2},\,Xe{F_2}$
C. $Te{I_2},\,Xe{F_2}$
D. $I{F_2}^ - ,\,Xe{F_2}$

Answer 1

Hint: Two compounds are said to be isoelectronic if they have the same number of electrons or the same electronic structure. Also, two compounds are said to be isostructural if they have the same geometry and structure.

Complete step by step answer:
Isoelectronic compounds are the compounds which have identical electron configurations, or in other words have the same number of electrons. On the other hand, isostructural compounds have the same structure, hybridization and shape. Isostructural compounds do not necessarily have the same cell dimensions nor the same chemical composition. Many minerals are isostructural when they differ only in the nature of a cation.
Now, in the given question, we need to investigate each option.
$I{F_3},\,Xe{F_2}$
The atomic number of Iodine = 53
The atomic number of Xenon = 54
And the atomic number of Fluorine = 9

Now,
Number of electrons in $I{F_3}$ = 53 + 3(9)
= 80
And the number of electrons in $Xe{F_2}$ = 54 + 2(9)
= 72
So, they are not isoelectronic

$BeC{l_2},\,Xe{F_2}$
The atomic number of bromine = 35
The atomic number of chlorine = 17

So, number of electrons in $BeC{l_2}$ = 35 + 2(17)
= 69
And the number of electrons in $Xe{F_2}$ = 72

Thus, they are not isoelectronic.

$Te{I_2},\,Xe{F_2}$
Atomic number of Tellurium = 52

So, number of electrons in $Te{I_2}$ = 52 + 106
= 158

And the number of electrons in $Xe{F_2}$ = 72

Thus, they are not isoelectronic.

$I{F_2}^ - ,\,Xe{F_2}$
Number of electrons in $I{F_2}^ -$ = 72
And the number of electrons in $Xe{F_2}$ = 72
So, they are isoelectronic.

Now, the hybridization of $I{F_2}^ -$ is . So, its geometry is trigonal bipyramidal. And the hybridization of $Xe{F_2}$ is also with the same geometry.

Hence, the correct answer is (D)

Note: Remember that there is a difference between isoelectric and isoelectronic. Isoelectric means having no net charge while isoelectronic means having the same electrons.