TOPIC 6 Groups In The Periodic Table Flashcards
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.
Test for hydrogen
Squeaky pop test. Put glowing splint in test tube of gas. If it makes a popping sound, hydrogen is present.
What color is the flame when an alkali metal is put in water?
Lilac
What are the group 7 elements?
Halogens: Fluorine Chlorine Bromine Iodine Astatine
All have 7 outer electrons
What type of molecule are halogens? What are their bonding?
They are diatomic molecules joined by covalent bonds which gives both atoms a full outershell.
What happens as you go down group 7
The melting point/boiling points increases. Reactivity decreases, this is because bigger atomic radius mean that there’s less force of attraction between the nucleus and outerelectrons and so less attraction to attract an extra electron to maintain a full outershell.
Chlorine characteristics and how do you test for it?
Fairly reactive, poisonous green gas.
It will turn damp blue litmus paper momentarily red (as Cl is acidic) and then bleach it white.
Characteristics of bromine
Poisonous, red, brown liquid that gives off an orange vapour at room temperature.
Characteristics of iodine
Dark grey crystalline solid which gives off purple vapor when heated.
Metal + halogen
(Reacts vigorously) > metal halide (salt)
Halogen + hydrogen
> hydrogen halide
What are group 0?
Noble gases are helium, neon, argon, krypton, xenon, radon
Characteristics of noble gases
Are all colourless, inert gases at room temp. They are monatomic. Nonflammable. Hard to observe. Low density.
Why are noble gases inert?
Because they contain a full outershell so have no need to gain/lose electrons to maintain a full outershell.
What are noble gases used for?
ARGON is used in filament lightbulbs as it provides and inert atmosphere and so will stop the v hot filament from burning up in the air.
The same principle is used in camera bulbs with argon, krypton and xenon to stop the flash filament from burning up in high temp flashes.
ARGON and HELIUM can be used to protect metals that are being welded as it stops the hot metal from reacting with the oxygen.
HELIUM is used in airships and party balloons as He has a lower density than air which makes the balloon float, it’s also nonflammable so is safer to use than hydrogen.
What happens as you go down group 0?
Melting/boiling points and density INCREASE as you go down group 0. Reactivity is the same throughout as they all have full outershells.
