The Alkali Metals

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What group are the alkali metals in?

Group 1 

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What are the properties of the Alkali metals?

  • they are very reactive 
  • soft to cut 
  • they are stored in oil 
  • the outside of them are dull ( such as a non metal ) 
  • when you cut into them they are silver and shiny ( like a metal ) 
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Why are they sorted under oil?

because they are very reactive and react with water and oxygen 

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What happens to them as you go down the elements?

  • they become more reactive
  • they become softer 
  • the melting points decrease
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Reaction with oxygen

When alkali metals are left in oxygen the surface will tarnish ( go dull ) 

Example of reaction : 

Lithium + oxygen --> Lithium oxide

Li + O2 --> Li20

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Reaction with water

They all have the same reactions and extras:

Lithium 

  • movers across the surface of the water
  • Fizzes 

Sodium 

  • melts when hits the water and turns into a sphere ( ball ) 

Potassium 

  • Catches a lilac flame 
  • spits at the end 
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reaction with water equation

Sodium + water --> Sodium hydroxide + Hydrogen 

Na + H20 ---> NaOH + H2

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What group are the halogens in?

Group 7

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What are unique about the halogens?

They go round in pairs 

' Diatomic Molecules '

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what happens as you do down the halogens?

  • their melting and boiling points increase 
  • their reactivity decreases 
  • they become darker in colour 
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reaction with group 1 metals

example of when a halogen reacts with an alkali metal 

lithium + fluorine --> lithium fluoride

2Li + F2 --> 2LiF

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Reaction with iron

Fluorine 

Fluoride is very reactive, iron burst into flames without being heated 

Chlorine 

iron and chlorine react fiercely, iron is heated first 

Bromine 

iron and bromine react, this reaction has to be heated 

Iodine 

iodine reacts with iron, has to be heated strongly 

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Testing Compounds

Compounds like sodium chloride, potassium iodide are called salts, they are made up of crystals 

the first name of a salt is always a metal ( positive ion ) 

the surname is always a non metal ( negative ion ) 

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Testing for metal ions ( flame test )

  • dip a piece of nichrome or platinum wire into the salt 
  • place into the hottest part of a blue flame #
  • look carefully at the flame and observe the colour change 
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the results of the flame test

contains sodium the flame goes orange/yellow

contains potassium the flame goes lilac/pink

contain lithium goes scarlet red 

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testing for chlorides bromides and iodides

  • place a small spatula of the salt into a test tube 
  • add a pipette of diluted nitric acid 
  • shake the test tube 
  • add a pipette of silver nitrate solution 
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results of chlorides bromides and iodides

white precipitate for chloride 

cream precipitate for bromide 

pale yellow precipitate for iodide 

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