Question

Which of the following pairs of compounds is isoelectronic and isostructural ?

• A. BeCl₂, XeF₂
• B. TeI₂, XeF₂
• C. Ibr₂^-, XeF₂
• D. IF₃, XeF₂

Answer 1

The Correct Option is C

To determine which of the given pairs of compounds are isoelectronic and isostructural, we need to understand two key concepts:

• Isoelectronic Compounds: These are substances that have the same number of electrons or the same electronic configuration.
• Isostructural Compounds: These are substances that have the same shape or molecular geometry.

Firstly, let's calculate the total number of electrons in each of the compounds:

1. BeCl₂:
   • Beryllium (Be): 4 electrons
   • Chlorine (Cl): 17 electrons each
   • Total for BeCl₂: \(4 + (2 \times 17) = 38\) electrons
2. XeF₂:
   • Xenon (Xe): 54 electrons
   • Fluorine (F): 9 electrons each
   • Total for XeF₂: \(54 + (2 \times 9) = 72\) electrons
3. TeI₂:
   • Tellurium (Te): 52 electrons
   • Iodine (I): 53 electrons each
   • Total for TeI₂: \(52 + (2 \times 53) = 158\) electrons
4. Ibr₂^-:
   • Iodine (I): 53 electrons
   • Bromine (Br): 35 electrons
   • Extra electron due to negative charge: 1 electron
   • Total for Ibr₂^-: \(53 + 35 + 1 = 89\) electrons
5. IF₃:
   • Iodine (I): 53 electrons
   • Fluorine (F): 9 electrons each
   • Total for IF₃: \(53 + (3 \times 9) = 80\) electrons

From the above calculations, only XeF₂ and Ibr₂^- have similar numbers of electrons. Let's verify their structures:

• XeF₂: Linear structure due to steric number of 5 (2 bond pairs, 3 lone pairs), VSEPR notation AX₂E₃.
• Ibr₂^-: Linear structure as per VSEPR theory due to similar steric number configuration, also following AX₂E₃ notation.

Both compounds, XeF₂ and Ibr₂^-, are indeed isoelectronic and isostructural, making option Ibr₂^-, XeF₂ the correct answer.