technique. Moseley then proceeded to rearrange the elements according to increasing atomic numbers. Moseley's arrangement seemed to clear up the contradictions and inconsistencies of Mendeleev's arrangement.

In a periodic table, the elements arranged in vertical columns are known as Groups. The elements arranged in horizontal rows are known as Periods.

Group 1 is also called the Alkali Metal group. These are strong Metals that are unusually soft and very reactive toward oxygen forming oxides and water forming hydroxides of the metal. These elements are so reactive toward oxygen and water vapor that they are stored under an inert liquid to protect them from oxygen and water vapour.

Group 2 is called the Alkaline Earth Metals. These metals are not as soft as Group 1 metals. They also react more mildly with oxygen to produce oxides of the metals and only react with water at temperatures where the water is steam.
Groups 3-12 are referred to as the Transition Metal groups. These metals are not as predictable because of the shielding effect of the inner electrons.

Groups 1-2 and 13-18 are referred to as the Representative Elements. Group 17 is referred to as the Halogen Group. Group 18 is referred to as the Noble Gas Group (previously known as the Inert Gas Group).

There are two special series of Elements that occur right after the transition metal element Actinium (Actinides) and Lanthanum (Lathanides). These special inner transition state metals were first rearranged by Dr. Glen Seaborg of University of California at Berkeley in the 1950's.

The metals which tend to have their atoms losing electrons during a chemical change are roughly found to the left Group 14. Non-metals which tend to have their atoms gaining electrons during chemical change are roughly found in Group 16-17 with some elements in the lower parts of Groups 15. Metalloids which tend to have their atoms sometimes losing and sometimes gaining electrons during chemical change are generally found in Groups 14-16. The Noble gases really belong to their own category since their atoms tend neither to lose or gain electrons.

As you proceed to the left in a period or as you proceed down within a group:

• The Metallic Strength increases (Non-Metallic Strength decreases).
• The Atomic Radius increases.
• The Ionization Potential decreases.
• The Electron Affinity decreases.
• The Electronegativity decreases.