1. CHEMICAL BONDING

2. Electrons and Chemical Bonding
Atoms combine by forming ionic, covalent, and metallic bonds.

3. Combining Atoms through Chemical Bonding
Chemical bonding is the joining of atoms to form new substances.
After bonding, the properties of the new substances are different than the properties of the elements that come together in the bond.
Chemical bonds form whenever valence electrons are shared, gained, or lost.

4. Electron Number and Organization
The number of electrons in an atom can be determined by looking at the atomic number.
The atomic number tells you the number of protons. Atoms are neutral, so the number of protons must therefore equal the number of electrons.
The electrons are organized into energy levels. Depending on the type of atom, there may be anywhere between 1 and 7 energy levels.
Only the electrons in the outermost energy level, the valence electrons, get involved in chemical bonds.
When looking at the periodic table, remember that all members of a group have the same number of valence electrons.