1. Chemical Formulas and Equations
Chapter 9 – 2
Part 1

2. Chemical Formulas
A chemical formula is a shorthand way to use chemical symbols and numbers to represent a substance.
A subscript is a number written below and to the right.
It tells how many atoms are in this molecule.
If there is no subscript, then there is just one atom.
C6H12O6
Glucose

3. Some Basic Rules
When you have two elements, you have two words in the name
The first word is the first element.
The second word is the second element.

4. Continued The second word also ends in “IDE”.
Like oxygen becomes oxide.

5. Writing Formulas for COVALENT COMPOUNDS
Covalent compounds are often composed of nonmetals.
The names of many covalent compounds use prefixes.
Example: Carbon Dioxide & Dinitrogen monoxide
CO2
N2O

6. Here are the first ten prefixes:
Mono- 1
Hexa- 6
Di- 2
Hepta- 7
Tri- 3
Octa- 8
Tetra- 4
Nona- 9
Penta- 5
Deca- 10
Prefixes Used in Chemical Names

7. Writing Formulas Covalent Compounds
Use the name of compound to write its formula
Ex: Carbon Dioxide
No prefix on first atom indicates 1 atom
The prefix di indicates 2 oxygen atoms= CO2
Prefixes always used on second atom C0 =
carbon monoxide
What is the formula for dinitrogen trioxide?
––> N2O3

8. More Practice 1. Dihydrogen monoxide 2. Silicon dioxide
3. Carbon monoxide
4. Hydrogen bromide
1. H2O
2. SiO2
3. CO
4. HBr

9. LET’S TRY IT! SiF4 Silicon tetrafluoride SF6 Sulfur hexafluoride N2O5
Dinitrogen pentaoxide