What are free electrons?

Hint – Begin by describing what the structure of an atom looks like, then move on to explaining how electrons are normally bonded to the nucleus and then provide the concepts of free electrons in detail.

Complete step by step answer:
To understand free electrons, let’s first focus on what the proposed structure of an atom looks like. An atom contains a nucleus, which is formed by protons (positively charged) and neutrons (neutral). The atom also contains electrons (negatively charged), that revolve around the nucleus. The electrons are bound tightly to the nucleus by electromagnetic forces that hold the electrons in well-defined orbits.

The energy and angular momentum of an electron in an orbit is always constant.

Free electrons – The electron in the orbit can only get out of their orbits, when energy (greater than threshold energy) is supplied to the electrons. These electrons are called free electrons, what we mean by free electrons are electrons that can move around in the crystal lattice which forms the element or any substance. So, to be clear even further, the electron cannot exit the crystal lattice.

One may wonder now, if an electron is moving out of the atom, how the element does not change with it. Well, the answer is quite simple, consider we provide energy to an electron, it gets excited, and moves on to the next atom. The electron then passes its energy to a new electron in the new atom and the new electron exits the atom to move on to the next atom and the original electron settles down in its place. This is how free electrons help in conducting electricity in conductors.

Note – It was previously mentioned that when energy is supplied, they move out of their orbits and become free electrons. But, it is not the case with non-conductors. Non-conductors cannot conduct electricity and this is because they have less or zero free-electrons that cannot conduct electricity in a material.