Question

how can we tell which d orbitals are involved in hybridisation of IF7

Answer 1

The involved d-orbitals are 5d₍xy₎, 5d₍xz₎, and 5d₍yz₎.

Answer 2

Solution:

For IF₇ the geometry is pentagonal bipyramidal, so the seven bonding directions must be matched by seven appropriately‐directed hybrid orbitals. In the traditional description, iodine “expands its octet” by forming sp³d³ hybrids using its 5s, 5p, and 5d orbitals. To decide which 5d orbitals participate, we compare the spatial orientations of the iodine 5d orbitals with the directions of the fluorine atoms. A group–theory (symmetry) analysis shows that only those d orbitals having lobes along (or in between) the directions toward the bonding sites can mix effectively. Typically if we choose the z‐axis along the principal axis (joining the two axial fluorines), the equatorial plane oriented fluorines are best reached by the d orbitals whose lobes lie in the x–y and the off–axis regions. In this common scheme the three available 5d orbitals are

• 5d₍xy₎,

• 5d₍xz₎, and

• 5d₍yz₎.

These orbitals have the proper orientations (after an appropriate rotation if necessary) so that when combined with the 5s and 5p orbitals they provide seven hybrid orbitals directed towards the seven fluorine atoms.

Thus, by matching the molecular symmetry and the spatial orientations of the iodine 5d orbitals, we deduce that the 5d₍xy₎, 5d₍xz₎, and 5d₍yz₎ orbitals are involved in the sp³d³ hybridization of IF₇.

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Summary Explanation (minimal):

• IF₇ is pentagonal bipyramidal (7 bonds).

• Iodine forms sp³d³ hybrids using its 5s, 5p, and three 5d orbitals.

• Using symmetry, only those 5d orbitals with lobes pointing toward the ligand positions (namely 5d₍xy₎, 5d₍xz₎, and 5d₍yz₎) combine with the other orbitals.

Details:

• Subject: Chemistry
• Chapter: Chemical Bonding & Molecular Structure (NCERT, Hypervalency)
• Topic: Hybridization (including d-Orbital Participation), Molecular Geometry, Group Theory Analysis