Covalent Bonding

Covalent Bonds

Occur when atoms of relatively similar EN share electrons.

Not good conductors. Solids tend to have low melting points. Generally liquid or gas at room temperature Form molecular substances whose shapes can

be predicted using VSEPR.

Naming Molecular Compounds

Unlike ionic compounds, molecules are named by using prefixes to state the exact number of each atom in the compound.

1= mono 2= di 3= tri 4= tetra 5= penta 6= hexa 7= octa 9 = nona 10 = deca

Name the following compounds:

NF3 PCl5 Cl2O7

Write the following formulas:

Diboron hexahydride

Nitrogen triiodide

Carbon disulfide

Formation of Covalent Bonds

Covalent bonds complete the valence shell of nonmetals.

Point of maximum attraction of nuclei for electrons.

Single bonds are the result of sharing two electrons.

Sigma Bonds

Single covalent bonds are sigma bonds.

Result from the overlap of an s-s, s-p, or p-p orbital.

σ

Multiple Bonds

Many molecules need to share more than one pair of electrons to form an octet.

Pi bonds result from the sideways overlap of p orbitals

π

Strengths of Covalent Bonds

As the number of shared pairs increases, bond length decreases.

Triple bonds are the shortest. Energy needed to break bonds is called

dissociation energy. Breaking bonds requires energy to be added.

Higher the bond energy, stronger the bond

Lewis Structures

Used to represent the physical arrangement of atoms in a molecule.

Based on a central atom with enough bonds to complete the octet of each atom.

Draw Lewis structures for the following molecules:

CO32-

CH2F2

NO3-

H3PO4

H2Se

VSEPR

Valence Shell Electron Pair Repulsion Theory

Way to determine shape of molecules in three dimensions.

Shapes will minimize electron pair repulsion.

VSEPR ShapesTable

VSEPR Shapes

Draw a table in your notebook with the following columnheadings:

VSEPR Structure Atoms around Lone Ex.shape Central atom Pairs

Draw the Lewis structure and predict the VSEPR shape of each of the following:

H2S

CO32-

PCl3

SiH4

SeBr6

hybrid orbital tutorial

Polar Molecules

Molecules are considered polar when they have polar bonds and there is an uneven distribution of charge.

The polarity of a molecule can be determined by looking at the central atom.

If the molecule has lone pairs on the central atom or it is not symmetric, the molecule is polar.

Determine the polarity of the following molecules:

H2S

CO32-

CCl4

PF3