Electron and Nucleus Atom contains skin and nucleus. Skin of atom contains number electrons and has negative charge. These electron moves around the nucleus on rounder orbit shape. This order of every orbit only can have a certain electron with certain rule, that every orbit can contain maximum electron 2 n2 (n = number of orbit that is counted from the nearest to the nucleus). So the first orbit can only have 2 electrons, the second orbit can have maximum 8 electrons, and so on.
Nucleus or center of atom have positive charge; on the nucleus have proton and neutron. This proton and neutron can't move to other atom. As example for atom hydrogen have one electron, one proton and one proton. As electron theory proton have positive pole, neutron don't have charge or neutral. Between proton and neutron is bound tightly. Actually the condition on the atom is look like the formation of solar system in the universe. Electron always circle atomic nucleus like planets encircle the sun. Bigger rotation circle also bigger energy. The electron circle nucleus 300.000.000 meter/second, this is amazing speed for electron that is very small. Although an atom can own a lot of electron but in rotation electrons encircle the atomic nucleus never colliding each other, because every electron rotate in their path. Free Electron On the atom sometimes have free electrons that are located in the outer of the electron circle path and have farthest distance from the nucleus.
This electron can move to other couple atom and become the group of this atom to circle other nucleus atom. The properties of this electron called free electron. Free electron usually available on the metal material; such as iron, copper, silver, gold etc. Non metal material such as glass, ebonite, wood, mica, etc, has no free electron. On the electric matter this free electron has an important role in conducting electric current.