Identify the number of valence electrons of an element using its position in the periodic table. The periodic table is arranged such that the column number in which an element is located identifies the number of valence electrons of that atom. This excludes the transition metals as they might have some inner shell electrons that count as valence electrons. For example, sulfur, designated by the symbol S, is located in column 6A. Thus, a sulfur atom contains 6 valence electrons.
Draw the electrons, represented as dots, around the symbol of the element. This is done by envisioning the element symbol as having four sides that are each capable of holding two electrons. Then, add the electrons one by one in a clockwise or counterclockwise fashion ensuring that each side has at least one electron before adding a second electron to a side. Using the sulfur example, start at the top with a single electron and continue adding electrons in clockwise fashion until all 6 of the valence are used up. The sulfur electron dot diagram will have two sides containing two electrons and two sides containing only one electron. The electron dot diagrams for sulfur and other common elements are provided in the resources section.
Determine the significance of the electron dot diagram. As per the Octet Rule, an element tends to form bonds in an attempt to fill its outer valence shell. Sulfur contains 6 valence electrons, which means that it needs 2 additional electrons to complete its octet. Therefore, sulfur readily forms bonds with elements that can share two electrons. For example, dihydrogen sulfide, or H2S, is composed of a sulfur molecule and two hydrogen molecules which each have a single electron to share, thereby completely filling sulfur's valence shell.