How to Read

The Periodic Table is one of the most useful tools in all of chemistry. Thus, it is essential that one can understand what information it holds. Each box contains information held about a certain element and is organized like this:

• Atomic Number - Simply refers to the number of protons present in the atom.
• Element Symbol - This is the symbol that chemical formulas or equations use to indicate that certain element. It is very important to know what symbol refers to what element, so it is highly recomended to memorize some of the most common symbols.
• Atomic Mass - The average mass of one atom of that element in amu's (Atomic Mass Units). It is average because different isotopes of the same element have different masses.

Grouping

The periodic table is brocken into several groups who have similar chemical properties. The beauty of the table is that even though an element may belong to several different groupings, most of the time all of them can be seen in one table by looking at the rows columns and sections.

Columns work from left to right and element all in the same column are said to be in the same family. Here are the names which refer to the different common families:

• Column I A- Alkali Metals
• Column II A- Alkaline Earths
• Columns III B through I B - Tranistion elements
• Column VII A - Halogens
• Column 0 - Noble Gases

Most of the elements in the same family have similar reactive qualities. For instance all of the noble gases are for the most part very unreactive with all other elements or molucules. Likewise all of the halogens are known for their reactive qualities. The reason for the similarity of reactiveness is because all of the elements in a family have the same tendincies to either lose or gain a certain number of electrons.

Rows work from top to bottom and are refered to as periods. They are distictive because of their weights and the energy levels of orbitals. As one looks along a row of the Periodic Table that is where one can see the closest atomic mass occuring.

Electron Configuration

Another function of the periodic table is to indicate into what orbitals elctrons will fill at what time. The left 2 columns will fill the s orbital first, so after H and He and the first two columns the electron configuration would look like this:

The first number indicates the energy level, the letter indicates the orbital type and the raised number indicates the number of electrons. After the break the p orbitals begin to fill, starting with Boron. Leaving us eventually with:

Thus we now have 8 electrons which satifies the octet rule and is the electron configuration for Ne, a noble or inert gas. Since neon is in no need for extra or fewer electrons, it does not need to share or take from other atoms. Thus it is not likely to bond with anything else. The pattern continues until we reach Sc which is where the d orbitals begin to fill. It looks like:

The d orbitals are what fill in the transition elements. Typically those are the only orbitals you need to know for Chem I.