1. A Review of Atoms
                                                              

2. The Atom The atom is the building block of all substances.
The basic parts of the atom are; the electron, the proton and the neutron.
Here’s a closer look at the atom.

3. The Proton Found in the nucleus. Positive charge.
Number of protons=atomic number.

4. The Neutron Found in the nucleus. Has mass, but no electrical charge.
About the same size as the proton.

5. The Electron
Note that the electron is found outside of the nucleus.Here it is shown as a small dot circling the nucleus.
There are the same number of electrons and protons in a neutral atom.

6. Energy Levels
Electrons are found in energy levels that surround the nucleus.
Each energy level has a letter designation (k to q).
There is a maximum number of electrons found in each level.
K(1st)=2, l(2nd)=8, m(3rd)=8 and n(4th)=2
Note that only elements to atomic number 20 are shown in this way.

7. Atomic Models
Atoms may be shown in different ways. This type of model is called the Bohr model.
This one is for sodium-atomic number 11.
Here is another example of the Bohr Model.