Maintaining electrical balance
In most elements, the number of electrons is equal to the number of protons. This maintains an electrical balance in the structure of atoms since protons and electrons have equal, but opposite electrostatic fields.

free electrons

Pictured here is an atom of copper, which is much more complex than either an atom of hydrogen or helium.

  The copper atom has 29 protons in its nucleus with 29 electrons orbiting the nucleus. Notice that in the copper atom, the electrons are arranged in several layers called shells. This is to graphically represent that the electrons are at different orbits or energy levels within the atom. The energy of an electron is restricted to a few particular energy levels. The energy is said to be quantized, meaning that it cannot vary continuously over a range, but instead is limited to certain values. These energy levels or shells follow a very predictable pattern. The closest shell to the nucleus can have up to 2 electrons. The second shell from the nucleus can have up to 8 electrons. The third shell can have up to 18 electrons. The fourth shell can have up to 32 electrons, and so on. Atoms can have this many electrons, but they do not have to have this many electrons in each shell. The greater distance between the electrons in the outer shells and the protons in the nucleus mean the outer shell electrons experience less of a force of attraction to the nucleus than do the electron in the inner shells.  


  1. Atoms have their electrons arranged in layers called shells.
  2. In order to maintain electrical balance the number of electrons is equal to the number of protons in most elements.
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