Covalent Bonding and Electron Geometry

(VSEPR)

• Why do atoms form single, double and triple bonds?

• How are the strength of a covalent bond, its bond length, and its bond dissociation energy related?

Essential Questions for Unit on Covalent Bonding

• What are the basic steps used to draw Lewis Structures of covalent compounds?

• Why does resonance structures occur, and what are some resonance structures?

• Which molecules are exceptions to the octet rule, and why do these exceptions occur?

• What is the VSEPR bonding theory?

• How can you use the VSEPR model to predict the shape of, and the angles in , a molecule?

• What is hybridization?

• How is electronegativity used to determine bond type?

• What are the characteristics of covalently bonded compounds

How atoms form single, double or triple bonds?

Sigma bonds (σ bond) – usually a single bond or the first bond in the double

and triple bonds. Pi bonds (π bond) – is an overlap of the p orbitals and makes up the second or

third bond in double and triple bonds.

Ethane C2H6

1

C1 has 4 single bonds. C1 is sp

3 hybridized. C1 has 4 sigma bonds.

2

Ethene C2H4

1

• C1 has 2 single bonds and 1 double bond.

• C1 is sp2 hybridized. • C1 has 3 sigma bonds and 1 pi bond.

2

Ethyne C2H2

1 2

• C1 has 1 single and 1 triple bond. • C1 is sp hybridized. • C1 has 2 sigma and 2 pi bonds.

VSEPR Model VSEPR (valence shell electron pair repulsion) • Electron pairs repell each other to achieve the greatest distance in three dimensional space.

Covalent Bonding of Beryllium

BeCl2

Linear

Covalent Bonding of Boron

BF3

Trigonal Planar

Covalent Bonding of Carbon

Tetrahedral

Triangle on Four Faces

Covalent Bonding of Expanded Phosphorus

PF5

Trigonal Bipyramidal

SF6

Octahedral