Which of the following pairs of compounds is isoelectronic and isostructural ?
- TeI2, XeF2
- IBr2-, XeF2
- IF3, XeF2
- BeCl2, XeF2
Answer
(2) IBr2-, XeF2
Solution
XeF2: 2 bond pairs + 3 lone pairs (sp3d) ⇒ linear.
TeI2: 2 bond pairs + 2 lone pairs (sp3) ⇒ bent ⇒ not isostructural.
IBr2-: 2 bond pairs + 3 lone pairs (sp3d) ⇒ linear ⇒ isostructural with XeF2.
IF3: 3 bond pairs + 2 lone pairs ⇒ T-shaped ⇒ not isostructural.
BeCl2: 2 bond pairs, no lone pair (sp) ⇒ linear ⇒ same (linear) shape as XeF2.
Isoelectronic check (total valence electrons):
IBr2-: 7 + 2 7 + 1 = 22; XeF2: 8 + 2 7 = 22 ⇒ isoelectronic.
BeCl2: 2 + 2 7 = 16 ⇒ not isoelectronic with XeF2.
∴ IBr2- and XeF2 are both isoelectronic and isostructural (linear).
Answer: (2)