Electron-Dot Diagrams

The Electron-Dot Diagram

An electron-dot diagram is a way to represent the surface electrons for an element. The surface electrons are the electrons that come into contact with other elements during chemical reaction. They help define the chemical and physical properties of the element, and the compounds formed from the reacting elements. The electron-dot diagram is determined by the number of electrons found in the valence shell of an element. More specifically, the electrons found in the s and p sublevels of the valence shell.

The Electron-Dot Diagram Example One: Carbon

The first step in the process is to detemine either the orbital-filling or electron-configuration diagram. For example, carbon contains six electrons in its electron-configuration diagram: [He]2s²2p². [He] represents two of the six electrons. Only four of the six electrons are in the valence shell. In this case, the valence shell contains just the 2s and 2p sublevels, two electrons in the s sublevel and two more in the p sublevel. The s and p sublevels to be diagrammed must be from the valence shell. The electron-dot diagram has four positions in which to place dots, with one postion each to the left, top, right and bottom of the symbol for the element. Two dots, representing two electrons at most, can be in each of the four postions.  The sum of electrons in the 2s and 2p is four electrons for carbon. This means  four dots will be in the electron-dot diagram. Two dots to the left, one above and one to the right of the symbol for carbon. See figure 1. No element will have less than one dot or more than eight dots in its completed electron-dot diagram. There are just eight possible electron-dot diagrams on the periodic table. With sufficient practice, the electron dot diagram for any element can be determined by locating the element's position on the periodic table.

The Electron-Dot Diagram Example Two: Aluminum

Aluminum has 13 electrons. Its electron-configuration diagram is [Ne]3s²3p¹. [Ne] represents ten of the 13 electrons. The valence shell contains two electrons in the 3s and one electron in the 3p. The sum of electrons in the 3s and 3p is three. This means three dots will be in the electron-dot diagram, with two dots to the left and one dot above the symbol for aluminum. See figure 2.

Electron-Dot Diagram Example Two: Bromine

Bromine has 35 electrons. Its electron-configuration diagram is [Ar]4s²3d¹⁰4p⁵. [Ar] represents 18 of the 35 electrons. See figure 3. There are 17 valence electrons in the 4s, 3d and 4p sublevels. Two of the electrons are in the 4s, ten electrons are in  the 3d and five electrons are in the 4p. The electron-dot diagram will display only the electrons in the s and p orbitals of the valence shell. The sum of electrons in the 4s and 4p is seven. This means there will be seven dots in the elecron-dot diagram.  Two dots to the left, two dots above, two dots to the right and one dot to the bottom of the symbol for bromine. See figure 3. The d or f sublevel electrons are not represented in the electron-dot diagram.

© Pat Thayer 2014-2016