JEE Main 2022 · 28 July · morning · Numerical answer · +4 / −0
The number of interhalogens from the following having square pyramidal structure is :
ClF₃, IF₇, BrF₅, BrF₃, I₂ Cl₆, IF₅, ClF, ClF₅
Answer and solution
Answer 3
Solution
Chemistry ma’am · 3 steps
Square pyramidal means 5 bond pairs and 1 lone pair: in interhalogens, that is the XF₅ type.
- Count electron pairs. The central halogen has 7 valence electrons. Each bond to a terminal halogen uses one of them, and the rest pair up as lone pairs. So for XYₙ, lone pairs = (7-n)/2.
- Shape we want. Square pyramidal comes from 6 electron pairs (octahedral arrangement) with 5 bond pairs and 1 lone pair. The lone pair takes one corner of the octahedron.
Molecule Bond pairs + lone pairs Shape ClF 1 + 3 linear ClF₃, BrF₃ 3 + 2 T-shaped ClF₅, BrF₅, IF₅ 5 + 1 square pyramidal IF₇ 7 + 0 pentagonal bipyramidal I₂Cl₆ 4 + 2 on each I square planar around each I, planar dimer - So. Only ClF₅, BrF₅ and IF₅ are square pyramidal, so the answer is 3.
The common slip: 4. Counting I₂Cl₆ as well gives 4. Each I there has 4 bond pairs and 2 lone pairs, which makes it square planar, not square pyramidal.
The idea to keep. For interhalogens XYₙ, lone pairs on X = (7-n)/2. Then XY₃ is T-shaped, XY₅ is square pyramidal and XY₇ is pentagonal bipyramidal.
Answer from the NTA final answer key. Solution by PrepWiser.