1. How Atoms Combine

2. Compounds
A compound is a molecule made up of two or more different atoms or elements
Ex.) H2O = compound – molecule of water
For most elements they are stable when the outer energy level is full
A state of stability is achieved by most elements by chemical bonds
Chemical bonds are forces that hold elements together in a compound

3. Covalent Bonds This is a bond when elements share electrons
A molecule is composed of two or more atoms are held together by covalent bonds

4. Polar Molecules These are covalent that do not share electrons equally
Water is the best example

5. Ions Not all atoms bond by sharing electrons
Bonds can be created by an element gaining or losing valence electrons
An atom that gains or loses an electron is a charged particle called an ion
In general, an atom that has less then 4 valence electrons will lose their electrons
When an atom loses its’ electrons it becomes positive (Ca+2)
When an atom has more then 4 valence electrons it will gain their electrons
When an atom gains electrons it becomes negative (O-2)

6. Ionic Bonds
Positive and negative ions are attracted to one another (opposites attract)
The attractive forces between two ions of opposite charge is called an ionic bond