1. Covalent Bonding
April 30, 2019

2. Matter in Nature
Matter exists in MANY different forms with MANY different properties.
STRUCTURE helps to determine properties.

3. Unbonded substances
Some substances exist as single atoms…they do not bond..
For example: noble gases

4. Chemical bonding
We know that atoms can join together to form molecules. But what joins the atoms to each other in a molecule? What is the “glue” that holds the molecule together?

5. Remember Ionic Bonds
Ionic bonds are one type of “glue” that holds elements with opposite charges.
Ionic bonds were classified by electrostatic forces holding them together. A positive charge is “attracted” to a negative charge, and vice versa.
For example: SALT
Smallest unit is Formula Unit

6. Covalent bonds
Covalent bonds are a sharing or more like a “tug-of-war” or fight (vs. a “glue”) for electrons between two atoms, rather that an attraction of opposite electrical charges.
Looking at the word:
Co- = being with or together
Valere = Latin, meaning very strong

7. Chemical Bonding Video

8. Covalent Bonds
So in covalent bonds, there are going to be two electrons that share with one other to form a very strong bond.
For example: Water, CO2
Smallest unit of a covalent compound is a molecule.
Typically occurs between 2 NON-METALS

9. Ionic vs. Covalent Bonds

10. Covalent bonds
Sharing of electrons

11. Molecular Formulas
Molecular formulas show how many atoms of each element a molecule contains.
H2O
CO2
C6H12O6
Covalent molecules can consist of more than 2 elements.
Not always written in lowest whole # ratio
For example: C2H6

12. Molecular compounds
Many non-metals exist in nature as molecules even though they are made up of one element.
There are 7 key ones, they are:
H2, Cl2, Br2, F2, I2, N2, O2
These are called diatomic molecules.
Their names are the same as their element name.

13. Diatomic Chlorine

14. A molecular formula does NOT tell you about the structure of the molecule.
Will not tell the arrangement of the atoms or who is bonded to whom (especially in the case of 3 or more elements)

15. Writing and Naming Molecular Formulas/Compounds
To write the formula, you need to know the compound’s name.
To write the compound’s name, you need to know the formula.
Important to know the numeral prefixes!!

16. You need not worry about charges or crisscrossing tricks!
Writing and Naming
Prefix must go on both elements UNLESS the 1st one is a mono-
See notes for the numerical prefixes
2nd element will end in –ide
CO2—NOT monocarbon dioxide
P4S3 Tetraphosphorus trisulfide
You need not worry about charges or crisscrossing tricks!

18. Naming
You also need to know which element to put first in the formulas and names of these compounds. Generally, they are in the same left-to-right order that they have on the periodic table.
Would need to know this only if the name or the formula is not given.

19. Write the Name SO3 CO SiO2 CF4 SF6 P3Br5 Sulfur trioxide
Silicon dioxide
SF6
Sulfur hexafluoride CO
Carbon monoxide
CF4
Carbon tetrafluoride
P3Br5
Triphosphorus pentabromide

20. Write the Formula Nitrogen triiodide Carbon disulfide
CS2
Phosphorus pentachloride
PCl5
Diboron hexahydride
B2H6

21. Some just have special names
F2 = fluorine gas
H2O = water
C12H22O11 = sucrose
H2O2 = hydrogen peroxide
NH3 = ammonia
CH4 = methane
CH3OH = methanol