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==Key Stage 3==
===Meaning===
A [['''Group]] ''' is a column on the [[Periodic Table]] with [[element]]s with the same number of [[electron]]s on the [[Outer Shell]].
===About Groups===
: The [[element]]s are arranged [[group]]s '''groups''' of similar [[Chemical Property|chemical properties]].
: [[Element]]s have similar [[Chemical Property|chemical properties]] when they have the same number of [[electron]]s in the [[Outer Shell]].
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====Trends within groups====
The [[Chemical Property|chemical properties]] of [[element]]s within a [['''group] ''' are similar. However, the [[reactivity]] within a [['''group]] ''' changes as you move up or down the [[Period (Chemistry)|period]]s.*[[Group 1]]: The [[Alkali Metal]]s all react strongly with water. The [[reactivity]] increases as you go down the [['''group]]'''.*[[Group 2]]: The [[Alkali Earth Metal]]s all react strongly with steam and acids. The [[reactivity]] increases as you go down the [['''group]]'''.*[[Group 7]]: The [[Halogen]]s all act as bleaching agents and kill bacteria. The reactivity decreases as you go down the [['''group]]'''.
*[[Group 0]]: The [[Noble Gases]] are all inert (unreactive).
The [[Physical Property|physical properties]] of [[element]]s within a [['''group]] ''' are similar. However, the property changes gradually as you move down the [['''group]]'''.