HL Bonding

HL BondingHL Bonding

HL BondingHL Bonding

Sigma & pi bondsSigma & pi bonds

and bonds

This goes beyond the Lewis representation

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals Remember -

s orbitals are what shape?

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals Remember -

s orbitals are what shape? Spherical

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals Remember -

s orbitals are what shape? Spherical

p orbitals are what shape?

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals Remember -

s orbitals are what shape? Spherical

p orbitals are what shape? Peanut-shaped

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals Remember -

s orbitals are what shape? Spherical

p orbitals are what shape? Peanut-shaped

d orbitals are what shape?

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to

form molecular orbitals Remember -

s orbitals are what shape? Spherical

p orbitals are what shape? Peanut-shaped

d orbitals are what shape? Doughnut-shaped

and bonds

This goes beyond the Lewis representation Considers the combining of atomic orbitals to form

molecular orbitals Remember -

s orbitals are what shape? Sphericalp orbitals are what shape? Peanut-shapedd orbitals are what shape? Doughnut-shaped

We will only consider s & p orbitals here

s orbitals are spherical p orbitals are dumbbell (or peanut) shaped

From: http://www.grenvillescience.com/chemistry/y6l/asdef.html

Sigma () bonds A bond situated symmetrically between 2 atoms

Sigma () bonds A bond situated symmetrically between 2 atoms Formed when 2 orbitals overlap along a line

drawn between the 2 nuclei

Sigma () bonds A bond situated symmetrically between 2 atoms Formed when 2 orbitals overlap along a line

drawn between the 2 nuclei Occurs when 2 s orbitals overlap

Sigma () bonds A bond situated symmetrically between 2 atoms Formed when 2 orbitals overlap along a line

drawn between the 2 nuclei Occurs when 2 s orbitals overlap e.g. H2

From: http://www.grenvillescience.com/chemistry/y6l/asdef.html

Occurs when an s orbital overlaps with a p orbital E.g. HCl

From: http://www.webchem.net/notes/chemical_bonding/orbitals_and_covalent_bonds.htm

Occurs when an s orbital overlaps with a p orbital E.g. HCl

Occurs when two p orbitals overlap “head on” E.g. Cl2, methane - CH4

From: http://www.webchem.net/notes/chemical_bonding/orbitals_and_covalent_bonds.htm

Pi () bond Formed by the “sideways” overlap of two p

orbitals The overlap occurs both above and below the line

drawn through the nuclei E.g. ethene C2H4

From: http://www.everyscience.com/Chemistry/Physical/Theories_of_Bonding/.images/MolStcPiBond.gif

From: http://www.cofc.edu/~deavorj/102/images/organic/pi-bonds.jpg

When & What Type?

A single bond is always a sigma bond as a pi bond cannot form until after a sigma bond has formed

A double bond consists of one sigma bond and one pi bond

A triple bond consists of one sigma bond and two pi bonds.

As the electrons in the pi bonds are further from the nucleus they are weaker than sigma bonds

e.g. ethene From: http://ibchem.com/IB/ibnotes/full/bon_htm/14.2.htm

The carbon-carbon double bond contains 1 and 1 bond. The carbon-hydrogen single bonds are all bonds.

The ethene molecule contains a total of one bond and five bonds

Identify the number of and bonds in the following molecules.Explain your answer.

Nitrogen Gas From:

“http://www.windows.ucar.edu/physical_science/chemistry/n2_molecule_sm.gif” cannot be displayed, because it contains errors.

A triple bond so one sigma and one pi bond

Identify the number of and bonds in the following molecules.Explain your answer.

Ethyne From:

http://www2.eou.edu/chemweb/molmodel/mmp9f.html

Identify the number of and bonds in the following molecules.Explain your answer.

Ethyne From:

http://www2.eou.edu/chemweb/molmodel/mmp9f.html

2 pi bonds in triple bond 3 sigma bonds - 1 in triple

bond and 1 in each of the carbon-hydrogen single bonds

Identify the number of and bonds in the following molecules.Explain your answer.

Buta-1,3-diene What is its formula? CH2CHCHCH2 From:

http://www.scibio.unifi.it/chimorg/cap04.html

Identify the number of and bonds in the following molecules.Explain your answer.

Buta-1,3-diene What is its formula? CH2CHCHCH2 From:

http://www.scibio.unifi.it/chimorg/cap04.html

Two pi bonds - one in each double bond

Eight sigma bonds - one in each of the double bonds (2) and one in each of the carbon-hydrogen single bonds (6)