What happens when elements react together?
They gain or lose electrons or sometimes they share electrons.
What are ionic compounds and how are they formed?
Ionic compounds are usually formed when metals react with non-metals. The oppositely charged ions are held together by strong forces of electrostatic attraction. The strong ionic bonds result in an arrangement called a giant structure or a giant lattice. A lot of energy is required to break the intermolecular bonds between the oppositely charged ions.
What does the formula of an ionic compound show?
This shows the ratio of ions present in the compound.
Ratio of a complex compound
2Mg(OH) (small 2) under the OH This compound shows that there are two magnesiums, 4 oxygens as 2x2 = 4 and 4 hydrogens (same reasons as oxygen).
Charges of ions
The charges of ions in an ionic compound always cancel each other out.
How are covalent bonds formed?
Covalent bonds form when atoms share pairs of electrons.
Substances containing simple molecules such as CH4 and H2O are simple molecules, they are held together by weak intermolecular forces and a small amount of energy is required to break the bonds.
Giant Covalent Structures
The giant covalent structures have huge numbers of atoms held together by networks of covalent bonds. These are sometimes called macromolecules. Diamond is a giant covalent structure. In diamond, each carbon atom forms four covalent bonds with its neighbours, this results in a rigid giant covalent lattice.
Metals are held together in layers with regular patterns. This means that crystals are formed.
Metal ions are arranged in a regular pattern with a lattice of positively charged ions. The outer electrons from each metal atom can easily move through the giant structure. The outer electrons form a 'sea' of free electrons surrounding positively charged metal ions. The strong forces of electrostatic attractions between the negatively charged electrons and the positively charged ions bond the metal ions together. These free electrons are called DELOCALISED electrons. They are not linked with any particular ion in the giant metallic structure.