Quick Recap: Chemical Bonding at 'O' Levels

1) Ionic bond: Formed between a metal and a non-metal.
It involves the transfer of electrons from a metal to a non-metal so that both can have noble gas configuration.

Ionic compounds have the following properties:

• High melting and boiling points, due to the strong electrostatic forces between oppositely charged ions, which require a lot of energy to overcome.

• Conducts electricity in molten (l) and aqueous (aq) states, but not in solid state. This is because in solid state, the ions are held in fixed positions in a lattice and cannot move around to conduct electricity. In molten and aqueous states, however, the ions are free to move around and carry charges.

• Soluble in water but not in organic solvents such as ethanol.

2) Covalent bonding: Sharing of valence electrons.

In covalent compounds, non-metals share their electrons so that each atom can have a noble gas configuration.

• Covalent bonds themselves are very strong. However, covalent compounds have low melting and boiling points. This is due to the weak intermolecular forces between the molecules, which require little energy to overcome.

Covalent compounds have the following properties:

• Covalent compounds cannot conduct electricity. They have no ions and no free electrons. Certain covalent compounds, however, can conduct electricity when dissolved in water. An example of such compounds would be acids. Hydrogen chloride (HCl) is a gas at room temperature, but dissolve it in water and you get hydrochloric acid. However, generally, covalent compounds cannot conduct electricity in whatever state.

• Covalent compounds don’t dissolve in water (with the exception of acids). They do dissolve in organic solvents.

3) Metallic Bonding: Bonding present WITHIN metal.
It consists of strong electrostatic forces between the positively charged metal ions and the delocalised electrons. The metallic structure consists of a lattice of positive ions in a sea of delocalised electrons.

• How a metal conducts electricity?

=>When a metal is used in an electrical circuit, the valence electrons entering one end of the metal causes a similar number of electrons to be displaced from the other end. The valence electrons move from the negative terminal to the positive terminal of the electric circuit.

The chemical bonding table Ms Jee gave was vey helpful.