Page "Metallic bond" Paragraph 15

Metal atoms contain few electrons in their valence shells relative to their periods or energy levels.

They are electron deficient elements and the communal sharing does not change that.

There remain far more available energy states than there are shared electrons.

Both requirements for conductivity are therefore fulfilled: strong delocalization and partly filled energy bands.

Such electrons can therefore easily change from one energy state into a slightly different one.

Thus, not only do they become delocalized, forming a sea of electrons permeating the lattice, but they are also able to migrate through the lattice when an external electrical field is imposed, leading to electrical conductivity.

Without the field, there are electrons moving equally in all directions.

Under the field, some will adjust their state slightly, adopting a different wave vector.

As a consequence, there will be more moving one way than the other and a net current will result.