THE PERIPHERY OF THE ATOMS: ELECTRONS

From the chemical point of view these are the most important particles, since the atoms form molecules by exchanging or sharing electrons. The molecules give also chemical reactions through this same procedure of exchanging or sharing electrons.


The electrons are found at the periphery of the atom. They have a very small mass and a tiny size as compared to nucleons.

Cartoon of electrons revolving around the nucleus

But why electrons are not attracted to the nucleus and collapse into it?
The electrons have negative electrical charge, exactly of the same amount but of opposite sign than protons. For this reason, atoms with all its protons and electrons are electrically neutral.





Because the electrons, placed at the periphery of the atom, have restricted zones of movement, called atomic orbitals.
  


S orbitals are spherical. In shell 1 there are only s orbitals. In shell 2 there are s and p orbitals. The latter have a shape similar to the outline of two balloons joined by the filler neck. In the following shells the type of orbitals and its form becomes even more complicated.


The orbitals here represented are actually superimposed around the nucleus. They are shown separately to increase the clarity of the drawing.
 Atomic orbitals are like air routes of airplanes that, although invisible, are fixed to avoid collisions. The further away from the nucleus, the more space the orbitals take.