Every chemist and chemistry student has seen the periodic table of the elements below:

The letters are the symbol of the element (Hydrogen is "H", Oxygen is "O"). These symbols are used everywhere. Some are obvious to the element ("H" is Hydrogen, "S" is Sulfur, "Ca" is Calcium), yet some aren�t so obvious ("Fe" is Iron, "Pb" is Lead "Na" is Sodium). In Chemistry, the symbols must have the same capitalization, usually first letter is capital, then second(if any) is lower case.(Sodium is Na, not na, NA, or nA; Chlorine is Cl, not CL, cl, or cL)

The number in each square is called the atomic number, it basically says how many protons are in the nucleus for these elements. (Hydrogen (H) has one, Oxygen (O) has 8, Sodium (Na) has11).

The larger number on the bottom is called the atomic mass. It is basically the number of protons and neutrons (average) for all the atoms of that element. (for example Oxygen�s atomic number is 16.00 because most Oxygen atoms have 8 protons and 8 neutrons.(We�ll get into it during the next lesson) It is used in stoichiometry which you will learn

There are some notable things that should be known about the periodic table:

• Metals are on the left, and non-metals on the right, they are separated by a staircase line going down from Boron(B) to Astatine(At)
• The 10 row wide, 4 row thick section in the middle are the transition metals they are a bit different from the rest of the metals (which will be explained in lesson #12)
• The two bottom rows are the Lanthanides, and Actinides They really fit between the metals on the far left and the transition metals, but put on the bottom so it wouldn�t make the periodic table super wide!
• Atoms that have the same group (in the same vertical row) originally have the same amount of electrons in their outer shell, (more will be explained in the next lesson)
• Atoms that have the same group also have very similar properties
• Atoms that have the same period (in the same horizontal row) have the same energy level outer shell (more will be explained in the next lesson)

For more info on the periodic table, including interesting facts on each element go to one of these links: