- Created by: Livy
- Created on: 07-10-13 18:26
How do they work?
Covalent bonds ar a result of electrostatic attraction between the positive nuclei and the negative (shared) electrons.
The group of atoms bonded together in this way is called a molecule.
The types and numbers of atoms in a molecule are shown in its formula.
Examples of covalent molecules
NameStructureModel Hydrogen (H2) Water (H2O) Ammonia (NH3) Methane (CH4)
Covalent compounds are usually gases or liquids with low melting points or boiling points and they don't conduct electricity.
Double bond = 2 shared electrons
Triple bond = 3 shared pairs
These occur when more than one pair of shells/orbitals overlap, resulting in multiple electrons being shared.
Multiple bonds are stronger then single bonds
A non-bonding atom (e.g. the two on the other side of the O when combined to make CO2) is called a lone pair.
Simple Covalent Substances
A Molecule = a group of atoms bonded with covalent bonds
The number of atoms is <100 (simple covalent substances)
Covalent molecules do not conduct electricity, as their particles are NOT charged.
Covalent compounds have no free electrons and no ions so they don't conduct electricity
Insulator/Non-conductor No charges on molecules, so no current can flow
Holding the shape together Covalent bonds holding them together&forces of attraction between layers
Low mpt/bpt Intermolecular forces are weak
Giant Covalent Structures
Van Der Waals = intermoleclar forces
They are weak, intermolecular BONDS are strong
Sand, diamond and graphite have millions of atoms joined by covalent bonds
The bonds in these substances don't form molecules but lattices (vast network/giant covalent structures)
An allotrope is a different structure of the same element
For example, carbon can form diamond or graphite, and they all have different properties because the structures aren't the same
Diamond Structures and Properties
Number of covalent bonds each atom forms: 4
Hardness: Very hard, because of structure
Electrical and thermal conductivity: Doesn't conduct electricity as no atoms can move
Graphite Structure and Properties
Number of covalent bonds each carbon atom forms: 3
Melting Point: Very high, as lots of bonds have to be broken
Hardness: Soft and slippery, layers of atoms can slide over eachother
Electrical and thermal conductivity: Conducts heat and electricity, as some atoms are free to move