Bonding in Covalent Molecules

Dispersion Forces Dipole-Dipole Attraction

Hydrogen Bonding

For information on these 3 types of bonding, see the word doc in the folder labelled ‘Types of bonding in covalent molecules’

Polarity and Shape of Molecule

Molecule Shape Polarity with reasons

Intermolecular Force

Methane For notes, see the Word doc in the folder labelled ‘Polarity and shapes of molecules’

Ammonia

Water

Hydrogen chlorideCarbon DioxideOxygen, Nitrogen molecules

Allotropes of Carbon

Diamond, graphite and buckeyballs (or fullerenes) are allotropes of carbon.

All 3 are made of C atoms but are arranged differently. Hence their properties differ.

For example, diamond does not conduct electricity but graphite does, etc.

Structures of covalent compounds and their properties.

1. Covalent Network Lattice

Example: Diamond Silicon Dioxide (or Quartz)

1. Covalent Network Lattice

Each atom is bonded to many other atoms by strong covalent bonds in a 3-D network lattice. As a result:

Have high mpts/bpts, hard, brittle, non-conductors of electricity and insoluble in water.

Covalent Network

Example: Diamond – is one giant structure (macromolecule). The C atoms are arranged in a tetrahedral position by strong intramolecular covalent bonds .

Covalent Network

Example: Quartz (Silicon Dioxide)

2. Covalent Layer Lattice

Example Graphite

In this type of structure, each atom is held by strong covalent bonds in a hexagonal position as a layer.

The layers are held by the weak dispersion forces. Hence the layers slide over each other; slippery

High mpts/bpts, layers slide, good conductors of electricity due to delocalised e’s between layers.

2. Covalent Layer Lattice

Example Buckeyballs

Are molecules of carbon arranged in a hollow sphere.

Most common one is called where the C atoms are arranged in hexagonal and pentagonal rings by strong covalent boding, shaped like a soccer ball.

Solids at room temperature, low mpts, soft and resistant to collision.

3. Discrete Molecules

Example Short molecules held by weak dispersion forces that break at low temperatures. (low mpts/bpts)

Non-conductors of electricity as they are neutral (no charges as they are SYMMETRICAL and hence non-polar molecules.)

Since they are non-polar substances, they will generally dissolve in non-polar solvents. LIKE dissolves LIKE.