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: The modern [[Periodic Table]] was arranged by a scientist called [[Mendeleev]]. Other's had tried to arrange all the [[element]]s before, but [[Mendeleev]] was the first to arrange by both [[Atomic Number]] and [[Chemical Propertiesof Elements|chemical properties]].: The columns of the [[Periodic Table]] are called [[Group]]s.: The rows of the [[Periodic Table]] are called [[Period]]s. {| class="wikitable"|-|[[File:PeriodicTable.png|center|900px]]|}