The electromagnetic force is strong so it is hard to separate electrons. The shell, as it is known, is not complete. The inner shell requires 2 electrons. When two hydrogen atoms are combined, the electrons want both nuclei to orbit them. Gaseous hydrogen at normal temperatures forms two atoms in H2.
There are several methods to separate electrons further apart. There is a fourth state, plasma, at very high temperatures (> 3000K), where electrons can be knocked off and nuclei are able to move independently.
Rubbish can be used to separate electrons from larger molecules where they are closer to the nucleus. Static electricity refers to the movement of electrons from outer orbits from one part to another. Static electricity causes shock by electrons moving back towards the nucleus, and thus a current flows.
An alternative method is to use electricity itself to separate electrons. This is what happens in cathode-ray tubes (e.g. This happens in cathode ray tubes (eg. computer chips.
There is an affinity for electrons to return to the nucleus.