GCSE Chemistry - Bonding

In any bond, particles are held together by electrical attractions between a positive charge and a negative charge

A covalent bond is a bond between two non-metals

In a covalent bond, a pair of electrons is shared between two atoms because both nuclei are attracted to the same pair of electrons

Covalent bonds are often shown with dots and crosses

e.g. Hydrogen molecules are said to be diatomic because the bond is so strong that hydrogen atoms are found joined together in pairs

Alkenes, Alkanes and Alkynes all have covalent bonds because they are made from non-metals

e.g. Nitrogen gas consists of triple bonds which are very hard to break. This is why nitrogen gas is very unreactive

Ionic bonding occurs between a metal and a non-metal

One of the atoms is is attracted to the electron pair much more strongly than the other one. The electron pair is then pulled very close to that atom, and away from the other one. In effect, one of the atoms has given it's electron to the other.

The charged particles are called ions

Ion - an atom that carries an electrical charge

Cation - carries positive charge

Anion - carries negative charge

Ionic bonding is where there has been a transfer from one atom to another to produce ions. The substance is held together by strong attractions between the positive and negative ions.

Most metals are hard and have high melting points so the forces between the particles are very strong.

In metallic bonding, the electrons are said to be delocalised. This means that the electrons are no longer attatched to a particular atom, instead, you can think of them as flowing around the whole metal.

Metallic bonding is sometimes described as an array of positive ions in a 'sea of electrons'.

In metallic bonding, we always think of the element as a whole structure so do not write them as ions in equations.

Intermolecular Forces - forces of attraction between separate molecules. They vary in strength from substance to substance.