Negatively charged building blocks of an atom that circle around the nucleus. Electrons are categorized as molecular particles that surround the nucleus of an atom. They are much smaller in size compared to the nucleus of the atom and usually negatively charged. Other than falling into orbits, electrons can be viewed as energy levels, which means they are not physical properties and can not be detected while orbiting around an atom. The fact that atoms themselves are incredibly small in size and require the most effective microscopes in order to see the atoms at the scale. Even in the off-chances that electrons can be seen, they move too quickly to be seen by the human eye. For this reason, scientists continue to be unable to ascertain the precise position of electrons, and have to settle for estimations.