In my essay on the structure and bonding in different substances, I am going to focus on electronic arrangement and their effects on the properties of the substance. .
METALIC BONDING.
Metallic bonding occurs between atoms with low electronegativity (.i.e. 1, 2 or 3 valence electrons); therefore there are many vacancies in valence shell. The crystal lattice of metals consists of ions NOT atoms. When electron clouds overlap, electrons can move into electron cloud of adjoining atoms. The outer electrons (-) from the original metal atoms are free to move around between the positive metal ions formed (+).
The metal is held together by the strong forces of attraction between the positive nuclei and the delocalised electrons. This is sometimes described as "an array of positive ions in a sea of electrons". There is a strong electrostatic force of attraction that two neighbouring nuclei have for the shared electrons between them. - This is the metallic bond. Each atom becomes surrounded by a number of others in a 3-D lattice, where valence electrons move freely from one valence shell to another. Each positive centre in the diagram represents all the rest of the atom apart from the outer electron, but that electron hasn't been lost - it may no longer have an attachment to a particular atom, but it's still there in the structure. Sodium metal is therefore written as Na - not Na+.
The physical properties of metals.
This strong bonding and the fact that the particles present in metals are tightly packed in the lattice results in dense, strong materials with high melting and boiling points. The strength, elasticity and ability to bend without breaking of many metals make them useful in construction. .
Metals are good conductors of electricity because these 'free' or delocalised electrons carry the charge of an electric current when a potential difference (voltage) is applied across a piece of metal. Copper, for example, is used to make the wire which goes inside electrical cables.
