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Definition: periodic table from Collins English Dictionary


1 a table of the elements, arranged in order of increasing atomic number, based on the periodic law. Elements having similar chemical properties and electronic structures appear in vertical columns (groups)

Summary Article: periodic table
from Philip's Encyclopedia

Arrangement of the chemical elements in order of their atomic numbers in accordance with the periodic law first stated by chemist Dmitri Mendeleyev in 1869. The metallic transition elements are arranged in the middle of the table between groups II and III. Alkali metals are in group I, and alkaline-earth metals in Group II. Metalloids and nonmetals are found from groups III to VII, with the halogens in group VII and the noble gases (inert gases) collected into group 0. The elements in each group have the same number of valence electrons and accordingly have similar chemical properties. Elements in the same horizontal period have the same number of electron shells. See table below

periodic table

Chemical elements are arranged according to their atomic number. The vertical columns, called groups, contain elements with similar chemical properties. The horizontal rows, called periods, are arranged in order of increasing atomic number and all elements in a row have the same number of electron shells. Elements coloured green in the table are non-metals; those coloured orange are metals; those coloured yellow are metalloid; those coloured blue, purple or pink are transition metals, the purple ones are the rare-earth elements, and the pink ones the transactinide elements.

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