Changes

*====[[Group 27]]: The [[Alkali Earth MetalHalogen]]s all react strongly with steam and acids. =========Chemical Properties=====: The [[reactivity]] increases of '''Halogens''' decreases as you go down the [[Periodic Table]].: '''groupHalogens'''all [[Chemical Reaction|react]] strongly as [[Bleaching Agent|bleaching agents]].*: '''Halogens''' all produce [[acid]]s when combined with [[Group 7Hydrogen]].: The '''Halogens''' are [[toxic]] to [[bacteria]] and are used in [[Halogendisinfectant]]s all act as bleaching agents and kill bacteria. {| class="wikitable"|-|[[File:Group7ElectronShells.png|center|100px]]| style="height:20px; width:500px; text-align:left;" |In a [[Chemical Reaction|chemical reaction]] an extra [[electron]] is added to the [[Outer Shell|outer shell]]. The [[reactivity ]] decreases as you go down the group because:*The outer [[electron]]s are further away from the [[Atomic Nucleus|nucleus]] with each additional [[Electron Orbital|electron shell]] making the [[force]] of [[attract]]ion weaker. This makes it less able to gain an extra [[electron]].*Even though the [[charge]] of the [[Atomic Nucleus|nucleus]] increases the outer [[electron]]s are shielded from most of the [[Positive Charge|positive charge]] of the [[Atomic Nucleus|nucleus]] by [[electron]]s in the [[Inner Shell|inner shells]].|}=====Physical Properties=====The [[Physical Property|physical properties]] of '''groupHalogens'''changes significantly as you go down the [[Periodic Table]]:*[[Fluorine]] - A yellow [[gas]] at [[Room Temperature|room temperature]].*[[Chlorine]] - A green [[gas]] at [[Room Temperature|room temperature]].*[[Bromine]] - A brown [[liquid]] at [[Room Temperature|room temperature]].*[[Iodine]] - A purple [[solid]] at [[Room Temperature|room temperature]].*[[Astatine]] -A dark purple [[solid]] at [[Room Temperature|room temperature]].: The [[density]], [[Melting Point|melting point]] and [[Boiling Point|boiling point]] all increase as you go down the [[Periodic Table]]. ====[[Group 0]]: The [[Noble Gases]] =========Chemical Properties=====: The '''Nobel Gases''' are all [[inert ]] (unreactive)because they have a full [[Outer Shell|outer shell]]. =====Physical Properties=====: The '''Nobel Gases''' are all [[gas]]es at [[Room Temperature|room temperature]].: The [[density]] and [[Boiling Point|boiling point]] all increase as you go down the [[Periodic Table]].