The Periodic Table

Brief History

Dmitri Ivancritch Mendeléeff came up with the first version of the periodic table in 1864. Since then more than 700 versions of the table have been proposed. The periodic table is organized by listing elements in order of increasing atomic mass. It is divided into vertical columns called groups or families and horizontal rows called periods. The lanthanide elements (row 6) and the actinide elements (row 7) are in most cases separated from the rest of the table by being placed beneath the table. Elements increase in their atomic masses as you move down rows of the table, but they change in their chemical properties.

The periodic table is divided into three main sections: the metals, the nonmetals, and the metalloids. Each one of these groups contains elements with similar physical properties.

Metals

Metals makeup more than 75% of the elements in the periodic table. Metals are characterized by the following physical properties.

1. They have metallic shine or luster.
2. They are usually solids at room temperature.
3. They are malleable. Malleable means that metals can be hammered, pounded, or pressed into different shapes without breaking.
4. They are ductile meaning that they can be drawn into thin sheets or wires without breaking. 5. They are good conductors of heat and electricity.

Nonmetals

There are 17 nonmetals in the periodic table, and they are characterized by four major physical properties.

1. They rarely have metallic luster.
2. They are usually gases at room temperature.
3. Nonmetallic solids are neither malleable nor ductile.
4. They are poor conductors of heat and electricity.

Metalloids

The six metalloids are B, Si, Ge, As, Sb, and Te. The properties of the metalloids have characteristics in between that of the metals and the nonmetals. They are good conductors of heat and electricity, but they are not good conductors or insulators.

Periodic Properties

The periodic table also has certain properties characteristic of certain regions in the periodic table.

Alkali Metals

These are the metals in the first column of the periodic table. They are soft shiny metals that usually combine with group VIIA nonmetals in chemical compounds in a 1:1 ratio.

Alkaline Earth Metals

These are the elements in the second column of the periodic table, and they are very similar to the alkali metals. They combine with the group VIIA nonmetals in a 1:2 ratio.

Halogens

The halogens are found in group VIIA. They are fluorine, chlorine, bromine, and iodine. The halogens exist as diatomic molecules in nature.

Noble Gases

The noble gases are also called rare gas elements, and they all occur in nature as gases. The noble gases make up the group VIIIA which is the last column in the periodic table. The noble gases fulfill the octet rule by having a full outer level with 8 valence electrons. Therefore, they do not undergo chemical reactions because they do not accept any electrons.

Transition Metals

The transition metals are the metals located between columns IIA and IIIA in the periodic table. The elements also have valence electrons in two shells instead of one.

Quiz

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Last Revised : Wednesday, December 10, 1997

This page was created by Guidry, Saitta, and Swan as a Chemistry 1201/2 class project.