TOPIC 6 Groups In The Periodic Table
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What type of reactions do group 7 elements take part in and why?
Displacement reactions as more reactive halogens displaces less reactive halogens in an aqueous solution of its salt.
Chlorine water+ potassium iodide
Potassium chloride + iodine
Write out the balanced equation for chlorine + potassium iodide
Cl2 + 2KI > I2 + 2KCl
What happens during halogen displacement?
An Electron is passed from the less reactive halogen to the more reactive halogen, meaning the less reactive ones are discharged and can exist as an atom.
What happens as you go down the halogen group and why?
Reactivity decreases as the outer-shell becomes further from the nucleus and so attraction decreases between nucleus and outer electrons so electrons are gained less easily.
Oxidation
Loss of electrons
Reduction
Gain of electrons
Oxidising agent
Accepts electrons and is reduced
Reducing agent
Donates electrons and gets oxidised
Redox reactions
Reactions where reduction and oxidation happen simultaneously.
Rusting word equation
Iron + oxygen + water > hydrated iron oxide (rust)
2 main ways to prevent rusting
Barrier and sacrificial method
Barrier methods
Painting/coating with plastic. Oiling/ greasing (when moving parts are involved)
Sacrificial method
Use a more reactive metal with it. (Coating or blocks)
Group 1?
Alkali metals >>> Lithium Sodium Potassium Rubidium Caesium Francium
Alkali metal + water
> > metal hydroxide (alkali) + hydrogen
How many outer-electrons do alkali metals have? What does this mean?
• This means that alkali metals are v reactive as are keen to give away their outerelectron and maintain a full outer shell. They then become a positive ion.
Physical properties of alkali metals
Low melting/boiling points in comparison to other metals. Very soft. Very reactive. Dull colored.
Balanced equation of lithium + oxygen
2Li + O2»_space; Li2O
What happens as you go down group 1? Why?
Alkali metals increase reactivity, boiling points and atomic radius. It also increases density. This is because, the larger an atom becomes, the further away the outer-electron is from the nucleus. This decreases attraction between the nucleus and outerelectron and so means the outerelectron is easier to remove (more reactive).
What type of reaction is alkali metals+ water?
Exothermic as it gives out heat. The flame is the hydrogen on fire.
Balanced equation of sodium + water
2Na + 2H2O »_space; 2NaOH + H2
How does an alkali metals period affect its reaction with water?
As you go down group 1, speed and violence of the production of metal hydroxide increases.
What color does the left over solution from alkali metals and water turn universal indicators?
Purple as its an alkaline solution.