1. Elements and Compounds

2. Pure Substance What does pure mean?
Unmixed
All the same
Uniform
A substance in which there is only one type of particle

3. Element
A pure substance that cannot be separated into simpler substances by physical or chemical means
MUST be on the periodic table
Gold – Au
Oxygen – O
Helium - He

4. Element or Not? Lead? Sugar? Steel? Brass? Water? Salt? Copper?
Yes! #82
Steel?
Brass? No
Water?
Salt?
Copper?
Chlorine?
Yes! #29
Yes! #17

5. Elements Each element has it’s own properties
Such as boiling point, melting point and density
Sodium
Chlorine

6. Categories of Elements
Metals
Shiny
Good conductors of heat and electricity
Malleable (sheets) and ductile (wires)
Most are solids

7. Categories of Elements
Nonmetals
Dull (not shiny)
Poor conductors
Brittle
Nonmalleable
Most are gas

8. Categories of Elements
Metalloids
Dull or shiny
Semi-conductors
Somewhat malleable and ductile

9. Compounds
A substance with 2 or more elements combined in a definite ratio

10. Compounds
A definite ratio does not change
O2 vs. CO2
CO2 vs. CO

11. Sodium Chloride (Salt)
Compounds
Compounds have a unique set of properties
Different than the elements that make it up + =
Sodium
Chlorine
Sodium Chloride (Salt)

12. Molecules
A molecule is formed when two or more atoms combine chemically.
All compounds are molecules but not all molecules are compounds.
H2 – Hydrogen – this is a molecule but not a
compound
H2O – Water – this is a compound