1. Atoms strive for 8 valence, so they bond
Bellwork 1. What is the octet rule? How do atoms reach it? 2. Which elements are exceptions to the octet rule?
Atoms strive for 8 valence, so they bond
H, He

2. 3. Remind me… What is an ionic bond?
A nonmetal takes electron(s)
from an atom of a metal

3. 23. Not all atoms gain or lose electrons. Sometimes they share
23. Not all atoms gain or lose electrons. Sometimes they share. This is called a covalent bond.
Ionic
Covalent

4. 24. A covalent bond occurs when two or more nonmetals share electrons to have a full outer shell.

5. 25. Which of the following are ionic and which are covalent?
Metal and nonmetal - ionic
CaCl2
CH4
H2O
NaF
Nonmetal and nonmetal - covalent
Nonmetal and nonmetal - covalent
Metal and nonmetal - ionic

6. Covalent Bonds
Covalent compounds have different properties from ionic compounds. They are often _________________ ______________ of varying colors, and they have very low __________________. They don’t usually ____________________ electricity well and do not typically ________________________ in water.
brittle
solids
Melting points
conduct
dissolve

7. Calculate electrons here
8. Let’s try drawing a Lewis structure for a covalent bond. Use the chart and fill in the steps.
Show the Lewis structure for PCl3 below.
Electron check!
Draw here
Calculate electrons here

8. Writing Lewis Structures
total
Find the ________ of valence electrons of all atoms in the molecule.
Use the ________________ to determine the number of valence electrons
Periodic table

9. Writing Lewis Structures
PCl3
(7) = 26

10. Writing Lewis Structures
least
The central atom is the ___________ abundant element that isn’t _____________.
Connect the outer atoms to it by __________ bonds, using a straight line. Each line represents the two electrons that are shared.
hydrogen
single

11. Writing Lewis Structures
Keep track of the electrons:
26  6 = 20

12. Writing Lewis Structures
outer
Fill the octets of the _______ atoms.

13. Keep track of the electrons:
26  6 = 20  18 = 2

14. Writing Lewis Structures
central
Fill the octet of the _______ atom.

15. Keep track of the electrons:
26  6 = 20  18 = 2  2 = 0

16. Writing Lewis Structures
If you run out of electrons before the central atom has an octet, form ___________ bonds (double or triple bonds only) until it does.
multiple

18. 9. Some atoms bond with a double bond. Let’s try one!
CO2
Carbon Dioxide ____________
Show the double covalent bonds in CO2 below.
Electron check!

19. 10. These are the steps for naming binary covalent compounds:
A. The nonmetal farthest on the left of the table is written first. (Except H)
Add prefixes to indicate number of atoms.
Never write the prefix “mono-” for the first element.
Change the ending to –ide for second element.

20. Molecular Nomenclature Prefixes
mono-
di-
tri-
tetra-
penta-
hexa-
hepta-
octa-
nona-
deca-
NUMBER 1 2 3 4 5 6 7 8 9 10

21. B. Mononitrogen trioxygen C. MonoNitrogen trioxygen
A. Nitrogen + oxygen
B. Mononitrogen trioxygen
C. MonoNitrogen trioxygen
D. Nitrogen trioxide (notice for oxygen, you drop the “y” and change to “i”!)

22. 9. Try these on your own! CCl4 N2O SF6 carbon tetrachloride
dinitrogen monoxide
sulfur hexafluoride