AP Chemistry – Class 52
- Period E – Thursday, January 10th
- Period F – Thursday, January 10th
Big Idea: How do atoms arrange themselves in a compound?
Lewis Dot Structures
- models – not “real”
- valence electrons only
- representative elements only
- formal charge determination
- multiple bonds
How To Construct Lewis Diagrams
- Place the least electronegative atom in the central position (except hydrogen), surrounded by the remaining atoms
- Calculate the total number of valence electrons available for the whole molecule or ion.
- If the species under consideration is a polyatomic ion add or subtract as needed
- Draw one line from the center atom to each of the outside atoms to symbolize a single bond.
- Subtract two electrons for each bond from the total number of valence electrons.
- Distribute the remaining electrons around their remaining atoms in such a manner as to best satisfy each atom
- Electrons that are not involved in bonding should be shown as lone pairs by drawing a single dot for each electron.
- At this point, identify if all of the atoms that are satisfied. (note: the octet rule only applies 100% for C/N/O/F)
- If there are too few electrons to satisfy every atom, replace one single bond with a double bond on the unsatisfied atoms.
- If your species is a polyatomic ion, put square brackets around your Lewis structure and place the overall charge of the ion on the outside of the square brackets.
- If your compound is ionic, then take electrons from the metal and move them to the non-metal. Draw brackets around each separately, with the appropriate charge on each.
- Ch. 9 (43 – 46)
- Note: determine formal charge of each atom