Chemistry: Halogens

Halogens are a group of elements found in group 7. They are all non metals, stinky and make salt.

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  • Created by: Livy
  • Created on: 19-03-14 19:10

Halogen Colours and States

Fluorine is a yellow gas

Chlorine is a green gas

Bromine is a dark orange liquid

Iodine is a dark purple solid

Fluorine is too highly reactive for general use.

Halogens are all simple molecular substances, but some of the Van Der Waals are stronger in some then others.

For example, Fl is smaller and has LESS I.M forces, so it is a gas

Iodine is bigger, and has MORE I.M forces, so it is a solid

Properties: Coloured, Brittle, Insulators, Low Density, React with Group 1

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Redox Reactions and Displacement

All Halogens are oxidising agents, and steal electrons from other things. All Alkali metals are oxidised and are the reducing agent. 

Halogen = Group 7 element

Halide = Ion of Group 7 element

A more reactive element will obviously displace a less reactive one. The most reactive one is Flourine, and the least is Astatine. 

In Hexane, the least reactive element will be the Halogen in the top layer. 

A more reactive Halogen will replace a Halide.

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Reactivity in the Group

As you go down, the rectivity decreases. This is because they increase in shells. The closer the electrons are to the nucleus, the easier it is to gain those electrons. 

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Halogens and Acids

Hydrochloric Acid - Hydrogen Chloride

Sulphuric Acid - Hydrogen Sulphate

Nitric Acid - Hydrogen Nitrate

These are all bonded covalently, so: H-Cl

When Dissolved in Water:

They become acids

All hydrogen halides form acids

Acids are ionic substances and break apart in water (dissociation)

Acid definition: Something that releases hydrogen IONS when in water 

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Reactions of Hydrogen Chloride

HCl can dissolve in water and organic solvents, in water he HCl molecules dissociate and H+ ions cause the soloution to become aciduc.

In organic solvents this doesn't happen and the HCl molecules remain bonded covalently. 

Magnesium + Hydrochloric Acid -> Magnesium Chloride = Hydrogen

Mg + 2HCl -> MgCl2 + H2

Calcium Carbonate + Hydrochloric Acid -> Calcium Chloride, Water and Carbon Dioxide

CaCo3 + 2HCl -> CaCl2 + Co2 + H2O

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Ionic Equations

Ionic Equations: Equations with the ions separated, where the ions that undergo no change are removed.

This can be done in steps:

HCl + NaOH -> NaCl + H2O

H+ + Cl- + Na+ + OH- -> Na+ + Cl- + H2O

H+ + OH- -> H2O

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