How does metallic bonding affect the properties of metals?

In the 1900's, Paul Drüde noted that the of metals are very loosely held. He visualized metals as an array of atomic cores (nuclei and inner electrons) or metal cations immersed in a “sea” of surrounding . In this model, the valence electrons are free, delocalized, mobile, and not associated with any particular atom.

1. The free electrons in the "sea" can absorb photons, so metals are opaque. Electrons on the surface can bounce back light at the same frequency as the light that hits the surface. Therefore, the metal appears to be shiny. This model accounts for the lustre of metals.

2. Since the electrons are free to move, if electrons from an outside source are added to a metal wire at one end, the electrons will move through the wire and come out at the other end at the same rate. Thus, this model accounts for the electrical conductivity of metals.

3. Metals usually have high densities. Hence the atoms are closely packed. That makes heat transfer by conduction more efficient. Conduction is the transfer of heat energy by vibration of particles to transfer energy from one end of the metal to the other end. Metals also have the sea of electrons to help them in this conduction. Since electrons are very small compared to the metal ions, they can easily pass through the spaces between the cations and help to transfer heat energy along. Thus, this model accounts for the thermal conductivity of metals.

4. The sea of electrons surrounding the cations act like a cushion and so, when the metal is hammered on, the overall composition of the structure of the metal is not harmed or changed. The cations may slide past each other, but the sea of electrons will adjust to the new formation of cations and keep the metal intact. Thus, this model accounts for the malleability and ductility of metals.