electron dot diagram

An electron dot diagram for an atom is a method of showing the way its electrons are distributed in the atom.

Here's a short list of how to make one:

1. Do an outer electron configuration for the atom.
2. Put the symbol for the atom in the middle, it represents the nucleus and the inner electrons.
3. Each dot represents an electron. Each side of the chemical symbol represents an orbital. The s orbital is to the right of the symbol. The px orbital is above the symbol, the py is to the left of the symbol, the pz is below the symbol.
4. Add dots as electrons as available in the following order:
5. Add the first two to the s orbital.
6. Add one to the px orbital.
7. Add one to the py orbital.
8. Add one to the pz orbital.
9. Add another to the px orbital.
10. Add another to the py orbital.
11. Add another to the pz orbital.

Here are some sample atom electron dot diagrams:

             •      •
  H•   K:    B:    •Si:

  •    ••    ••     ••
 •N:  •Po:  :Cl:   :Ar:
  •    •     •      ••

Ion electron dot diagrams are similar to their atomic counterparts. Here's how you do them:

1. Do the atomic dot diagram.
2. For negative ions, add dots until you get eight, and count the number that you add. For positive ions, count the dots and take them all away.
3. Enclose the ion diagram in brackets.
4. Indicate the charge by placing it to the right of the ion, near the top. The charge for negative ions will be the number of electrons you added followed by the - sign. For positive ions, it will be the number of electrons you took away followed by the + sign. If you only took away or added one electron, omit the number 1.

Here are some examples:

 __   __   __    __
 |     |+  |  ••  |2-
 |  H  |   | :Po: |
 |     |   |  ••  |
 ¯¯   ¯¯   ¯¯    ¯¯

Note that no specific electronic configuration information can be gleaned from drawing an electron dot diagram. One cannot assume that the seventh electron "went into" the p_y orbital. In order to know what electrons are in what orbital for a given element in a given compound, one must fully analyze the energy states of each of the orbitals into which electrons can be populated. For most nonmetals, VSEPR is a good model toward predicting compound geometry and electronic structure.