Covalent Bonding

A covalent bond is the sharing of two electrons and in simple covalent compounds, these electrons will come from two different atoms.

Through covalent bonds, atoms can share electrons to fill the valence shell, and obtain a full octet. In order to know how many electrons an atom needs to obtain a full octet, the electronic structure needs to be noted together with the number of electrons needed. An electron can share the same number of electrons that it needs to get a full valence shell.

Example

Hydrogen, H      1              needs 1 electron to get to             2

Carbon, C            2,4           needs 4 electrons to get to           2,8

Oxygen, O           2, 6          needs 2 electrons to get to           2,8

Nitrogen, N         2,5           needs 3 electrons to get to           2,8

Sulfur, S               2,8,6        needs 2 electrons to get to           2,8,8

Chlorine, Cl          2,8,7       needs 1 electron to get to              2,8,8

HCl

For example, both Hydrogen and Chlorine require 1 electron to have a full outer shell, and thus 1 hydrogen and 1 chlorine can react to form HCl

H₂O

In water, oxygen needs two electrons whilst hydrogen can only share 1 electron. This means that oxygen will require 2 hydrogens to get a full outer valence shell.

CO₂

In carbon dioxide, carbon needs 4 electrons whilst oxygen needs 2. This means that for carbon to be able to share 4 electrons it will need 2 oxygens, each of which giving 2 electrons.

Properties

Compounds tend to be made up of small molecules.

• In covalent compounds, there are strong bonds between different atoms but this means that the molecule is only made up of up to a few atoms.

Compounds tend to have low melting points and boiling points.

• As opposed to ionic compounds, there are no charges in covalent compounds, and this means that there is very little interaction between different molecules. The end result is that covalent compounds have low melting points and boiling points as it would be easy to break the interaction between different molecules.

Inorganic covalent compounds tend to have low densities.

• The lack of interactions between different molecules highly influences the packing of such compounds. Very little interactions mean that there will be more spaces between molecules decreases the amount of compound that can fit in a specific volume, decreasing the overall density.

These are insoluble in water.

• The lack of charge in covalent compounds means that these compounds do not dissolve in water.

They do not conduct heat or electricity.

• The lack of charge in covalent compounds means that there are no charges to transfer electrons and therefore covalent compounds do not conduct electricity. They also do not conduct heat.