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: '''Halogens''' all produce [[acid]]s when combined with [[Hydrogen]].
: '''Halogens''' are [[toxic]] to [[bacteria]] and are used in [[disinfectant]]s.
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|[[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]].
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===Physical Properties===
The [[Physical Property|physical properties]] of '''Halogens''' changes significantly as you go down the [[Periodic Table]]: