Lewis Dot Diagrams

Review How many valence electrons do most atoms want? 8 Who is the exception to this rule? Hydrogen & Helium

Review In a chemical bond, do alkali metals gain or lose electrons? In chemical bonds do metals form cations or anions? Cations In chemical bonds, do non-metals form cations or anions? Anions

Only show valence electrons One “dot” = one electron

Hydrogen Beryllium Boron H Be B Carbon Nitrogen Oxygen C N O

Illustrating Compounds Two types of compounds: Ionic Covalent Ionic = a metal bonded with a nonmetal Covalent = two nonmetals

Ionic Lewis Dot Diagrams In ionic bonds electrons are transferred Example: Sodium Chloride +1 -1 Na Cl Cl Na

Mg O Mg O Practice Illustrate a Lewis Dot Diagram for Magnesium Oxide: +2 -2 O

Covalent Lewis Dot Diagrams In covalent bonds electrons are shared. Lines are used to represent shared electrons One line means each atom is sharing one electron with the other (1 line = 2 electrons)

In an H2 molecule, each hydrogen shares its one electron with the other hydrogen. We illustrate this sharing with a line: H H

Illustrate a bond between two chlorine atoms: Cl Cl

Sometimes atoms need more than one electron to complete their outer shells. We call this a double bond and illustrate using two lines: O O

Illustrate a bond between two Sulfur atoms:

Occasionally an atom will need to triple bond to fill its valence shell. To illustrate triple bonds we use three lines: N N

Illustrate a bond between two phosphorus atoms:

Many compounds consist of more than two atoms How would we illustrate a Lewis Dot Diagram for a Phosphorus atom bonded to 3 chlorines?

The atom that needs the most electrons always goes in the middle!

How would we illustrate a Lewis Dot Diagram for a Hydrogen bonded to a Carbon and Nitrogen?