Periodic table

The periodic table of the chemical elements, also called the Mendeleev periodic table, is a tabular display of the known chemical elements. First created by Dmitri Mendeleev, the elements are arranged by electron configuration so that many chemical properties follow a regular pattern across the table. Each element is listed by its atomic number and chemical symbol. Mendeleev's ordering of the periodic table was one of the greatest developments in modern chemistry. Chemists were able to quantitatively explain the behavior of the elements, and to predict the existence of yet undiscovered ones. There are 116 chemical elements whose discoveries has been confirmed. Ninety four can be found naturally on Earth, and the rest have been produced in laboratories.

Groups

A group is a vertical column in the periodic table of the elements. There are 18 groups in the standard periodic table. Elements in a group have similar configurations of their valence shell electrons, which gives them similar properties. They can also be called families.

Related Topics:
Group - Valence shell

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Group numbers

There are three systems of group numbers; one using Arabic numerals (1, 2, ... 18), another using Roman numerals (I, II, ... VIII), and one using a combination of Roman numerals and Latin letters (IA, IIA, IB, ... VIIIA). The Roman numeral names are the original traditional names of the groups; the Arabic numeral names are a newer naming scheme recommended by the International Union of Pure and Applied Chemistry (IUPAC). The IUPAC scheme was developed to replace both older Roman numeral systems as they confusingly used the same names to mean different things.

Related Topics:
Group numbers - Arabic numerals - Roman numerals - Latin - International Union of Pure and Applied Chemistry

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Standard periodic table