1. QUIZ NEXT CLASS!!! Study all notes, classwork, and homework Topics:
Matter
Atoms
Pure substances
Mixtures
Elements – symbols
Compounds - formulas

2. Using Symbols and Formulas
TO DESCRIBE MATTER

3. Symbols – represent an element
Elements are represented using a 1 or 2 letter symbol
The first letter MUST be capitalized, and the second must be lowercase
Example: H = hydrogen, He = helium

4. Ex/ H2O
Formulas
subscript
Represents the smallest unit of a substance that still has the properties of that substance
Made up of symbols and subscripts
Symbols tell you what element(s) make up the substance
Subscripts tell you how many of each element make up the substance (they apply to the element they are AFTER
No subscript after an element means there is only one atom of that element in the substance

5. Example:
CH4
C = carbon, 1 atom
H = hydrogen, 4 atoms

6. AgNO3
Ag = silver, 1 atom
N = nitrogen, 1 atom
O = oxygen, 3 atoms

7. Practice
K2CO3
FeCO3
NaNO2
Na2SO4
NaHSO4

8. Honors: Parentheses
A polyatomic ion is a group of two or more atoms bonded together that then bond to another atom/group as a unit.
If there are more than one of these units bonded in a compound they are contained within parentheses and a subscript is used. The subscript is distributed to all of the elements in the polyatomic ion.
Ex/ Ca(NO3)2
Ca = 1
N = 1 x 2 = 2
O = 3 x 2 = 6