The electrons in an atom’s outer energy level are the electrons that are important to consider in
chemical bonds and chemical reactions. These electrons can be represented in a diagram called an
electron dot diagram. The outermost electrons are drawn as dots around the chemical symbol.
In this activity, you will draw electron dot diagrams for several elements.
1. Write the symbol for the element. For electron dot diagrams, this symbol represents the nucleus and all of the electrons of the atom except the outermost electrons. The symbol for chlorine is Cl. In an electron dot diagram, this symbol represents the nucleus and the ten electrons in the first two energy levels.
2. Use the periodic table to determine how many outer electrons the element has. Do this by finding to which group the element belongs.
Chlorine belongs to Group 17, the halogens, which have seven outer electrons.
3. Draw a dot to represent each electron in the outer level of the element. Two electrons can be placed on each side of the symbol. The first two electrons should be paired on the right side of the symbol. The rest of the outer electrons should be distributed counterclockwise one by one around the other sides of the symbol.
1. ions (anions) are formed when an atom gains electrons.
2. Positive ions (cations) are formed when an atom loses electrons.
2. The Lewis Structure (electron dot diagram) of each ion is used to construct the Lewis Structure (electron dot diagram) for the ionic compound.
Lithium fluoride, LiF1. Lithium atom loses one electron to form the cation Li+
2. Fluorine atom gains one electron to form the anion F-
3. Lithium fluoride compound can be represented as
1. In a covalent compound, electrons are shared between atoms to form a covalent bond in order that each atom in the compound has a share in the number of electrons required to provide a stable, Noble Gas, electronic configuration.
2. Electrons in the Lewis Structure (electron dot diagram) are paired to show the bonding pair of electrons.
3. Often the shared pair of electrons forming the covalent bond is circled
4. Sometimes the bond itself is shown (-), these structures can be referred to as valence structures.
1. Nitrogen atom has 5 valence electrons
2. Hydrogen atom has 1 valence electron
3. Each of the 3 hydrogen atoms will share its electron with nitrogen to form a bonding pair of electrons (covalent bond) so that each hydrogen atom has a share in 2 valence electrons (electronic configuration of helium) and the nitrogen has a share in 8 valence electrons (electron configuration of neon)
4. Lewis Structure (electron dot diagram) for ammonia