Orbitals
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Orbitals. … and more orbitals. When atoms are close together…. Atomic orbitals on each atom are affected by the presence of other atoms. Attraction of the other nuclei for the electrons in an atom pulls them into different volumes of space than they would be in, if the atom were isolated.

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Orbitals

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Orbitals

Orbitals

… and more orbitals


When atoms are close together

When atoms are close together…

  • Atomic orbitals on each atom are affected by the presence of other atoms.

  • Attraction of the other nuclei for the electrons in an atom pulls them into different volumes of space than they would be in, if the atom were isolated.

  • All atoms experience these changes.

  • We call this hybridization.


Let s consider carbon without hybridization

Let’s consider Carbon, without Hybridization

  • According to our energy level diagram, an isolated carbon atom has a full s, and two singlets in p orbitals, with one p orbital completely empty.


Orbitals

  • This means that only two covalent bonds can form: the singlets being attracted toward another nucleus, and an electron from that atom attracted toward the carbon.


Orbitals

  • The s orbital stays unshared. The two electrons in it repel all other electrons.


Orbitals

  • And, the last p stays empty UNLESS another atom (with an unshared pair) shares its own two electrons with carbon.


That s not what happens

That’s not what happens

  • Carbon will pull an electron from another atom into the empty orbital

  • And that other atom will pull one of carbon’s paired electrons into that orbital.

  • Another electron will be pulled into the remaining orbital.


Hybridization

Hybridization

  • All of this pushing and pulling changes the orbitals.

  • The four valence atomic orbitals hybridize into new orbitals.

  • These orbitals are not s orbitals, not p orbitals, but something in-between.

  • These are the most stable orbitals when there are additional atoms nearby.


Orbitals

Atomic orbitals hybridize

  • The new orbitals are equivalent, and of equal energy.

  • The four electrons split.

  • Carbon bonds to four separate atoms, forming four single ( bonds.


4 hybrid orbitals form

4 hybrid orbitals form

  • They all have the same energy and the same shape. They are fully equivalent.

  • Each of these orbitals has 1/4 s character and 3/4 p character.

  • Their energies are in-between those of the original s & p orbitals.

  • Their shapes are in-between those of the original s & p orbitals.


How to visualize hybrid orbitals

How to Visualize hybrid orbitals

  • They look like funny little lopsided p orbitals.

  • They point in 4 different directions, due to the repulsion between electron pairs.

  • They are called sp3 orbitals (from sppp)

http://ww2.educarchile.cl/UserFiles/P0001/Image/Mod_2_contenidos_estudaintes_ciencias_quimica/Quimica_cambio_6.jpg


Sp 3 hybrid orbitals

sp3 Hybrid orbitals

  • How do the orbitals fit together?

  • Tetrahedral arrangement

http://wps.prenhall.com/wps/media/objects/724/741576/Instructor_Resources/Chapter_01/Text_Images/FG01_12.JPG


What about double triple bonds

What about double & triple Bonds?

  • π bonds form from the overlap of perfectly parallel pure p orbitals.

  • Hybrid orbitals are not pure p orbitals

  • Hybrid orbitals do not form π bonds.


Double bonds

Double Bonds

  • One  bond and one π bond.

  •  bond forms when any two orbitals (including hybrid orbitals) overlap straight-on.

  • π bond only forms from pure p orbitals.

  • Atom hybridizes only 3 orbitals, not all 4.

  • The original s and two of the original p orbitals hybridize to form 3 identical orbitals.


3 hybrid orbitals form

3 hybrid orbitals form

  • They all have the same energy and the same shape. They are fully equivalent.

  • Each of these orbitals has 1/3 s character and 2/3 p character.

  • Their energies are in-between those of the original s & p orbitals.

  • Their shapes are in-between those of the original s & p orbitals.


More hybrid orbitals to visualize

More hybrid orbitals to visualize

  • They still look like funny little lopsided p orbitals.

  • They point in 3 different directions, due to the repulsion between electron pairs.

  • They are called sp2 orbitals (from spp)

  • The remaining p orbital forms the π bond.

Top view of 3 sp2 orbitals

http://image.tutorvista.com/content/organic-chemistry/sp2-hybridization-carbon-orbital.gif


Sp 2 hybrid orbitals

sp2 Hybrid orbitals

  • How do the orbitals fit together?

  • Trigonal planar arrangement


Triple bonds

Triple Bonds

  • One  bond and two π bonds.

  •  bond forms when any two orbitals (including hybrid orbitals) overlap straight-on.

  • π bonds only form from pure p orbitals.

  • Atom hybridizes only 2 orbitals, not 3 or 4.

  • The original s and one of the original p orbitals hybridize to form 2 identical orbitals.


2 hybrid orbitals form

2 hybrid orbitals form

  • They have the same energy and the same shape. They are fully equivalent.

  • Each of these orbitals has 1/2 s character and 1/2 p character.

  • Their energies are in-between those of the original s & p orbitals.

  • Their shapes are in-between those of the original s & p orbitals.


Still more hybrid orbitals to visualize

Still more hybrid orbitals to visualize

  • They still look like funny little lopsided p orbitals, but more s-like than the others.

  • They point in 2 different directions, due to the repulsion between electron pairs.

  • They are called sp orbitals

  • The remaining two p orbitals form 2 π bonds.

sp orbitals formed from s & p orbitals

http://www.cartage.org.lb/en/themes/Sciences/Physics/MolecularPhysics/ElectronicStructure/ChemicalBond/Moleculargeometry/fig6-17.jpg


Sp hybrid orbitals

sp Hybrid orbitals

  • How do the orbitals fit together?

  • Linear arrangement


Summary

Summary

  • When making only  bonds: atoms use sp3 hybridization

  • When making one π bond: atoms use sp2 hybridization

  • When making two π bonds: Atoms use sp hybridization


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