1. Elements and Compounds
Foothill Chemistry

2. Vocabulary Element Atomic Number Chemical Symbol Substance Compound
Chemical Change
Chemical Formula
Molecule

3. Element
A substance that cannot be separated or broken down into simpler substances by chemical means
All atoms of an element have the same atomic number
Elements are represented on the periodic table by their chemical symbol

4. Chemical symbols
Chemical symbols are 1-2 letter “abbreviations” for the element
The first letter (if there is more than one) is always capitalized
The second letter is not capitalized

5. Substance
A substance can be represented by a chemical formula to represent the atoms that it contains
All of the molecules are the same
No matter how large or small of a sample you have, the molecules will be the same molecule
A molecule is the smallest unit of a substance that keeps all of the physical and chemical properties of that substance

6. Chemical Compound Substance that contains more than one type of atom
Has to have at least two different atoms
The atoms have to be chemically bound together
The ratio of the atoms is shown by the subscripts in the chemical formula

7. Chemical Formula
A combination of chemical symbols and numbers to represent a substance
Can represent an element or a compound
Does not represent a mixture
H2O - Water
NH4 - Ammonia
CH3OH – Methyl Alcohol
SO2 – Sulfur Dioxide

8. Element vs. Compound One type of atom
Diatomic elements have two of the same atom in their molecules
More than one type of atom, chemically bound

9. Chemical Reaction
The process by which one or more substance change to produce one or more different substances
Reactants – Molecules you start with
Products – Molecules you get from the reaction

10. Mixture No chemical symbol to represent the mixture
There is more than one type of molecule found in a mixture
Multiple substances are found in a mixture

11. Classifying Matter