Formation of metallic bond • the metal atoms "lose" one or more of their outer electrons • These electrons become delocalized, and free to move throughout the entire metal. • These negative delocalized electrons hold the metal cations together strongly.
Metallic bonding in sodium • 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+ or potassium metal is written as K but not K+.
Metallic bond definition • It is the attraction force between positive metal ions and the delocalized electrons.
Metallic bond properties • Unlike ionic bonding, distorting the atoms does not cause repulsion so metallic substances are: • ductile (can be stretched into wires) • malleable (can be formed into shapes). • Heat and electricity conductivity. • The free moving electrons also allow for high thermal conductivity, and the electrons can carry the heat energy rather than it being transferred slowly through atoms vibrating.
Electrical conductivity of metals • Electric current is the flow of electrons in a wire. • In metals, the outer electrons of the atoms belong to a ‘cloud’ of delocalised electrons. • They are no longer firmly held by a specific atom, but instead they can move freely through the lattice of positive metal ions. Normally they move randomly. • when the wire is connected to a cell, they are pushed away from the negative terminal and drawn to the positive one. The cloud of electrons drifts through the wire