Sigma and Pi BondingSWBAT: Draw Quantum Mechanical models of molecules using sigma and pi bonding

Carbon HybridizationType of hybrid

Atomic orbitals

used

Number of hybrid orbitals formed

Number of atoms

bonded to the C

Aufbau Chart

sp3 s, p, p, p 4 4

sp2 s, p, p 3 3

sp s, p 2 2

Carbon HybridizationType of hybrid

Atomic orbitals

used

Number of hybrid orbitals formed

Number of atoms

bonded to the C

Aufbau Chart

sp3 s, p, p, p 4 4

sp2 s, p, p 3 3

sp s, p 2 2

sp3 Hybridization

Carbon HybridizationType of hybrid

Atomic orbitals

used

Number of hybrid orbitals formed

Number of atoms

bonded to the C

Aufbau Chart

sp3 s, p, p, p 4 4

sp2 s, p, p 3 3

sp s, p 2 2

sp2 Hybridization C2H4

Carbon HybridizationType of hybrid

Atomic orbitals

used

Number of hybrid orbitals formed

Number of atoms

bonded to the C

Aufbau Chart

sp3 s, p, p, p 4 4

sp2 s, p, p 3 3

sp s, p 2 2

sp Hybridization C2H2

Covalent Bonds The formation of a covalent bond involves

the overlapping of half filled atomic orbitals

The two different categories of covalent bonds are Sigma and Pi covalent bonds

Sigma bonding Bond is formed by the axial overlapping

of half filled atomic orbitals The electron cloud formed is

cylindrically symmetrical about inter nuclear axis

The electrons constituting sigma bonds are called sigma electrons

3 Types of Sigma Bonding1. s-s overlap2. s-p overlap3. p-p overlap

sp-overlaps Example: CH4

Strength of Sigma Bonds The strength of three types of sigma

bonds varies as follows p-p > p-s > s-s A p-p overlap is greater than an s-s

overlap allowing it to be stronger

Pi Bonding This type of covalent bond is formed by the

lateral or sidewise overlap of the atomic orbitals

The orbital overlap takes place in a way that their axes are parallel to each other but perpendicular to the internuclear axis

The pi bond consists of two charge clouds above and below the plane of the atoms involved in the bond formation

The electrons involved in the p bond formation are called pi electrons

Pi Bonding

Sigma and Pi Bonding

Sigma bonds are stronger than pi bonds (greater overlap between orbitals occurs)

Pi bonding between the two atoms is formed only in addition to a sigma bond (Sigma first then Pi)

Atoms rotate around sigma bonds but not pi bonds

The shape of the molecule is controlled by the orientations of sigma bonds around the central atom. Pi bonds are superimposed on sigma bonds.

Sigma and Pi bonding with Oxygen (O2) 1s22s22p4

s orbitals are filled and the 2px orbital is filled

The 2py and 2pz orbitals are partially filled An O=O molecule has one sigma and one

pi bond (connect both lobes of a p orbital for a pi bond…. Draw two lines for one pi bond)

Oxygen (O2) Nitrogen (N2)

Carbon Hybridization Review http://www.chemit.co.uk/resource/downl

oad/94