Lewis Dot Notation
Lewis Dot notation is a way of describing the outer shell (also called the valence shell) of an atom's electrons. Dots are drawn around the elements symbol to represent the electrons in the valence shell of the atom. For example Helium, which has two electrons in its valence shell, would be written as:
He has two electrons in an s orbital.
Al has 2 electrons in an s orbial and 1 in a p orbital. The three dots around the symbol stand for the three electrons. Al has 3 valence electrons (1s22s22p63s23p1). You can determine this by writing out the electron configuration or simply by the Roman numeral III at the top of the family on the periodic table containing Al. The dots are placed on all four sides of the symbol before repeating dots on a side. An example of this is the carbon atom which only has four electrons in its valence shell.
Note: C always makes four bonds; so one electron is promoted from the s orbital to the p orbital and C is represented as this:
Atoms will always promote electrons so they can make more bonds, thus increasing stability.
When the number of electrons in the valence shell is more than four electrons the dots are written as pairs on the side until all the electrons are accounted for. Examples are Fluorine and Sulfur.
