Lecture 20: Order of Repulsion and Hybridization Involving d Orbitals

NH3_{3} :: Electron Configuration of N

There is no Promotion required because there is no place to promote. Only 3 bonds can be formed. There is SP3^{3} hybridization but 1 hybrid orbital is holding the lone pair. The other 3 is to hold the hydrogen bond. The molecule is derived from Tetrahedral. But one orbital is occupied by a lone pair so it is Trigonal Pyramid and the angle is 107^{\circ}

Order of repulsion

LP - LP > LP - BP > BP - BP

  • When adding lone pairs the angle is smaller

Hybridization Involving d Orbitals

Promoting an electron from 3S to 3d orbital

AX5_{5} type molecule - Trigonal Bi pyramid - dSP3^{3}

SP3^{3}d2^{2} - 1 electron is promoted to d from 3S and the other from 3P

AX6_{6} type molecules - Octahedral Structure - d3^{3}SP3^{3}

Why isn't a double bond twice the energy of a Single bond?

Because a double bond is on π\pi bond and one O bond and π\pi bond is weaker.

Three unpaired electrons \rightarrow can form 3 bonds but it forms 5 bonds

To do this we promote the S electron to the 3d orbital then has 5 unpaired electrons.

Why can't this happen with NCIS_{S} ? Because it has 2S and 2P and there is no 2d orbital.

Now P undergoes dSP3^{3} hybridization to give 5 orbitals. Each one contains an unpaired electron. These hybridized orbital are directed to the corners of a trigonal bi pyramid (AX5_{5} )

Valence Bond Theory

Diamagnetic - All paired electrons, repelled

Paramagnetic - Unpaired electrons, attracted to magnetic field

All Paired electrons but is Paramagnetic (By Molecular Orbital Theory)

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