Hede.io Entry: Periodic Table of Chemical Elements

The periodic table is an arrangement of the known chemical elements. The elements are ordered based on their atomic number, electron configuration and recurring chemical properties. These properties establish periodic (occurring at intervals) trends.

The periodic table consists of groups and periods. A group is a column of elements in the periodic table. There are 18 groups numbered (the f-block columns between groups 3 and 4 are not numbered). Groups of elements in the same column have similar chemical and physical properties. A period in the periodic table is a horizontal row. All the elements in a period row have the same number of electron shells.

Around the time Russian chemist Dmitri Mendeleev first published the periodic table Mendeleev predicted 8 elements not yet then known to science to fill gaps in the periodic table. All those predicted elements were later discovered. Mendeleev's most accurate predictions concerned the properties of elements later discovered and named germanium, gallium and scandium.

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