1. Lewis Dot Structures Atoms and Ions

2. Why do we use them? To visualize • Valence electrons • bonding

3. Review: Valence electrons Valence electrons are those that are located in the highest (outermost) energy shell of an atom which varies from atom to atom. They are involved in bonding

4. Pattern of valence electrons in the periodic table • All elements in a particular group of the periodic table have similar properties and the same number of valence electrons. • Potassium has 1 valence electron. It is in group 1A or 1. • Bromine has 7 valence electrons. It is in group VIIA or 17.

6. Dot structures The element symbol represents the nucleus and the inner core electrons (non-valence). The dots represent the valence electrons. H•

7. Think….. • Why do we only show valence electrons on a Lewis dot structure?

8. How to construct a Lewis Dot Structure! • Draw the elemental symbol. • Determine the number of valence electrons. • Draw a dot for each valence electron around the symbol. It is customary to use two electrons on each side of the symbol (4 sides = 8 electrons, a full shell). **Note: it is customary to place two electrons on the right hand side if there are two or more valence electrons to show filling of the s-orbital or 1st energy level.

9. p+ p+ p+ p+ p+ p+ e- e- e- e- e- e- e- Carbon Atom • • C Elemental Symbol Valence Electrons Electron Dot Structure

10. Your turn! • Construct the Lewis dot structure for Gallium (Ga)

11. Gallium!! Ga

12. Lewis Dot Structures for Ions • Same method as before. • Valence electrons will change • Brackets indicate an ion • Charge is placed on the outside of the bracket S [ S ]2-