O.K., now most of chemistry deals with atoms, and how they react with each other right? So first, what is a atom?

Most of you know that an atom is matter (stuff) broken down to it�s smallest unit. Imagine, a person has a large tower full of Lego's, he then breaks them apart piece by piece. Each of the pieces is considerably an atom, because you can�t break a single Lego piece further without much effort.

Now, all atoms have similar properties (besides the fact of being really small)They all have a nucleus which contains protons and neutrons. Protons are positively charged particles, and neutrons are non-charged particles. The number of protons determine the element. For Example, oxygen always has 8 protons in it�s nucleus, and sodium always has 11 protons. The number of neutrons can vary in a single element. All atoms also have electrons around the nucleus. Electrons are negatively charged, and they are so small, that hey considerably have no weight. Electrons move around the nucleus in places called electron shells.

O.K., Now you know what these atoms are and what their made of, so here�s something else: Atoms always try to stay at the lowest energy possible. It�s like when a ball is rolled down a hill, the ball will roll until it is at it�s lowest point. So how can an atom achieve lower energy? Having a full or empty outer(or valence) shell of electrons. Now these shells can usually hold only 8 electrons, so the atom will want to obtain either 8 or 0 electrons in it�s outer shell. Now how can these atoms obtain or lose these electrons? Giving or getting electrons from other atoms of course!

You know from the last lesson that the periodic table is split into two sections. The left side has metals and the right side has non-metals. Now for this, completely ignore the transition metals in between and count the group from left to right.

These numbers not only label the group, but show how many electrons are in their outer(or valence) shells. Hydrogen(H), lithium(Li), sodium(NA), potassium(K), rubidium(Rb), cesium(Cs), and francium(Fr) all start out with one electron in its outer shell. Fluorine(F), chlorine(Cl), Bromine(Br), Iodine(I), and Astatine(At) all have seven electrons in its outer shell. You get the pattern? Here�s a chart to help you:

Here�s another thing, metals usually give up their electrons, and go to 0 in their outer shell, while non-metals usually obtain them, and go to 8 in their outer shell, This is called the Octet Rule, but lets save that for the next lesson.

Review:

• An atom is matter broken down to it�s smallest unit
• Protons are in the nucleus and have a positive(+) charge
• Neutrons are also in the nucleus and has a neutral or no charge
• Electrons are surrounding the atom in electron orbitals
• Atoms always try to obtain the lowest energy
• A low energy states that an electron can achieve lower energy by having either 0 or 8 in their outer shell