Free electrons

This is the answer chapter 3 owed you. Metals conduct because of what happens to the electrons in their outermost shell.

The outer electrons get loose

In the atoms of a metallic element, the electrons in the very outermost shell can leave easily. In a piece of metal, a huge number of electrons that have left in this way wander about at random in the space between the atoms.

Figure to be added

Figure 19.5 — metal atoms drawn as a regular array of positive metal ions, with the outermost-shell electrons shown loose in the spaces between them.

Free electrons

Electrons that have left their atoms and move at random through a metal are called free electrons.

Figure to be added

Figure 19.6 — the inside of a metal, with free electrons shown as dots and short arrows pointing in every direction, showing their random motion.

Random is not a current

Note what these electrons are doing before anything is connected: moving in every direction at once. As many go one way as the other, so nothing is carried anywhere and there is no current. A piece of copper lying on a bench is full of moving charge and is not carrying a current.

Why metals conduct

The reason a metal conducts electricity well is the presence of these free electrons. It is not that a metal is hard or shiny or dense — it is that a metal holds charged particles that are already free to move.

The atoms themselves stay put

Only the electrons move. What is left behind is a lattice of positive metal ions, fixed in place. In a copper wire carrying a current, no copper goes anywhere.