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Explanation:
The periodic table is a table that classifies elements based on their chemical properties and physical properties into groups (columns) and periods (rows). Elements in the same group have similar chemical properties, for example group I elements (alkali earth metals) have the same valency (electrons in the outermost energy level). The table also shows the physical properties of an element, for example whether it is a metal or a non metal; e.g group 1, 2 and 3 elements are all metals while group 4 are metaloids, group 5,6 and 7 are non metals and group 8 elements are noble gases with an octet configuration. Additionally, the table also reveals the order reactivity depending on the eas of gaining electrons (for non metals) and loosing electrons (for metals).