1. Elements, Compounds and Mixtures

2. Elements and Compounds
Element – a substance that contains only one kind of atom.
Compound – a substance that contains atoms of more than one kind joined together.
Mixtures – contains different types of particles that are not joined together.

3. Elements - Atoms and their Symbols
There are about 90 different types of atoms that occur naturally on earth.
There are a few more that can be made by nuclear reactions making about 100 elements in all.
The latest man made element is Uuo. Made by firing lead atoms at Krypton atoms. Only 3 atoms of ununoctium were made and they lasted less than a millisecond.

4. Atoms and their Symbols
Every atom has its own symbol;
C carbon
Co cobolt
Ca calcium
Cl Chlorine
The names may vary in different languages, but the chemical symbol in always the same.

5. Common Elements
The particles in most elements are individual atoms, but in some elements the particles are molecules;
Name
Symbol
Diagram
Formula
Description
Argon Ar
atoms
Iron Fe
Oxygen O O2
Molecule
(each with 2 atoms)

6. Mixtures and Compounds
Hydrogen and oxygen are elements.
If you put them together you have a mixture of elements.
If a flame is put in the mixture a chemical reaction takes place and a new substance is formed – a compound.
Hydrogen + oxygen water

7. Compounds There are over 20 million known compounds.
When a new compound is formed the properties are different from the elements that formed it.
Sodium + Chlorine sodium chloride
Very reactive poisonous salt