1. LECTURE 3.4 – LEWIS STRUCTURES

2. What are the types of ions that can form?

3. I. Ions When atoms gain/lose electrons, they gain a charge.
Ion – An charged atom due to unequal number of protons and electrons
Cation – A positively charged ion
Anion – A negatively charged ion

4. Cats make people feel positive
Way to remember the difference between a cation and an anion.

5. +1 +2 +3 ±4 -3 -2 -1

6. How do you draw Lewis Structures?

7. I. Lewis Dot Structures Bohr diagrams take too long to draw
Lewis Dot structures only show the valence electrons.
Group number (Group 1A, 2A, etc.) tells us the number of valence electrons

8. Class Example
Draw the Lewis structure for fluorine

9. Table Talk
Draw the Lewis Structure for Carbon

10. Stop and Jot
Draw the Lewis structure for Mg. What would the charge of a magnesium ion after the Octet Rule?

11. How do you show electrons being shared?

12. Lewis Structures for Ionic BondsNa Cl

13. Lewis Structures for Ionic Bonds
[Na]+
[Cl]-

14. Chemical Bonding
Ionic Bonds
Metallic Bonds
CovalentBonds

15. I. Covalent Bonding This is a bond between only non-metals.
In a covalent bond, the electrons are shared between the elements so that each can get an Octet.
Most molecules in biology are covalent compounds

16. II. Drawing Lewis Structures
Halogens and hydrogen form only one bond and are located at the end of a molecule.
The central atom is always carbon (if it is present) and/or the element that has the lowest electronegativity.

17. Class Example
Draw the Lewis structure for H2S

18. Table Talk
Draw the structure for NH3

19. Stop and Jot
Draw the Lewis structure for C2H6

20. III. Single, Double and Triple Bonds
Elements can share more then one set of electrons.
Also can form double and triple bonds.
Single bond = 2 electrons
Double bond = 4 electrons
Triple bond = 6 electrons

21. Class Example
Draw the Lewis Structure for CH2O

22. Table Talk
With your table, draw the structure of C2H2

23. Stop and Jot
Draw the structure of HCN