1. Chemical Symbols and Formulas
Chapter 2.7

2. Chemical Symbols
All elements in the Periodic Table have symbols that are recognized world wide.
It does not matter which country you are in or the language you speak.
Example: The element Iron is always identified by “Fe” and Oxygen is “O”.
The names are not always the same but the symbols are. “Fe” is iron in Canada, fer in France and fier in Romania.

3. Chemical Symbols
A Chemical symbol is an abbreviation of a name of an element.
Capital letter if only one letter.
Only first letter capital if more than one letter
Element
Chemical Symbol
Oxygen O
Nitrogen N
Hydrogen H
Sodium Na

4. Sodium comes from the word sodanum, a headache remedy, and it’s symbol (Na) comes from the Latin word Natrium.

5. Chemical Formulas
A chemical formula is the combination of symbols that represent a particular compound.
The chemical formula indicates which elements are present in the compound and in what proportions.
Ex. 1: Water molecule
H2O: 2 atoms of hydrogen, 1 atom of oxygen
Ex. 2: Iron Oxide molecule
Fe2O3: 2 atoms of iron, 3 atom of oxygen

6. Chemical Formulas - Examples
Calcium Carbonate (chalk) – CaCO3
Sodium Chloride (salt) – NaCl
Acetysalicylic acid (aspirin) – C9H4O8
Acetic acid (vinegar) – C2H4O2

7. Chemical Formulas NOTES:
- Each symbol in a formula represents an element.
- If only one atom of an element is present in the compound, no subscript is used.
- If more than one atom of an element is used, then the symbol is followed by a number indicating how many atoms are used. This is called the subscript.

9. Homework Do Questions #1–5 on Page 59 You may use your Periodic Table.
Make sure that for each question you write out that question first then you write your answer and then continue on to the next question and so on until completed.

10. 2 atoms of hydrogen (in a hydrogen molecule)
1 atom of sodium
2 atoms of hydrogen (in a hydrogen molecule)
3 atoms of magnesium
2 atoms of phosphorus
8 atoms of oxygen total atoms
3 carbon atoms

12. Tomorrow Go over counting atoms worksheet Pass in Homework
Chapter 2 quiz