Chemistry Section 2: Chemistry of the elements (COMPLETED)
Chemistry Section 2: Chemistry of the elements (COMPLETED)
The Periodic table
Groups are columns in the periodic table, the number of a group represents the number of electrons on an atom's outer shell.
Elements in the same group have the same number of electrons on their outer shell.
This means they will behave in a similar way; they will react and bond similarly.
For example in group one, the elements all form +1 ions as they each loose one electron to become stable (to have a full outer shell).
Periods are rows on the periodic table, the row represents the number of orbitals that a atom has.
To the left are the metals
to the right are the nonmetals
Nobel gasses are inert, this means they do not react.
The reason for this is because they are stable: meaning they have a full outer shell, so they do not need to loose or gain electrons.
Metals/ non metals
Metals are all conductors.
Metals form metal-oxides which are alkaline.
Nonmetals don't conduct.
They form nonmetal-oxides which are acidic.
Group 1 elements
reactions with water
The group one elements- lithium, sodium, potassium- are easily identifiable as the same group due to the fact that they all react vigorously with water (clearly due to the fact they have similar electronic configurations.)
The reactions that occur are huge- they get bigger further down the group. Hydrogen gas is produced as well as metal hydroxide.
Group one elements are more reactive further down the group.
Group one elements need to loose an electron- the one on the outer shell- to react.
electrons are held to an atom by the protons in the nucleus.
If an electron is close to the nucleus the force holding it in will be very strong, if it is further away it will be weaker.
So bigger atoms (towards the bottom of the group) with the outer orbital far from the nucleus will loose their electron more easily: this means they react more easily/quickly/more/vigorously.
Smaller atoms with the electron closer to the pull of the nucleus (at the top of group one) will be less reactive as it takes more to lose the electron.
Group 7 elements
Colours and physical states (at room temp
changes down group
We would expect the colour to keep getting darker and the melting and boiling points to keep getting higher further down the group.
Hydrogen chloride/ Hydrochloric acid
Hydrogen chloride gas is HCl
Hydrochloric acid is hydrogen chloride dissolved in water. The two ions become detached leaving Cl- and H+ ions. H+ is acidic, hence the term acid.
Water (H2O) is a polar molecule.
Methylbenzene is a non-polar molecule.
Hydrogen chloride is a polar molecule.
Polars only dissolve in polars.
When hydrogen chloride is dissolved you get +H ions. These are acidic.
Group 7 elements become less reactive as you go down the group.
At the top, the positive charge of the proton in the nucleus is close to the surface (as there are few shells) this makes it easy for them to pull in the one electron they need to become stable, meaning they are very reactive.
Lower down where there are more shells the pull of the proton is further from the surface making it less easy to pull in another electron.
Oxygen and Oxides
Copper, iron and phosphorus all react with air.
If you know the volume of air that you have, then react it with on of these, then re measure the volume of air; what has been lost is all oxygen that reacted.
Preparation of Oxygen
hydrogen peroxide is put in a conical flask with manganese(IV) oxide as a catalyst.
Hydrogen peroxide > water + oxygen
You can then collect oxygen by downwards displacement method.
The two non-metals (Carbon + Sulphur) burn in air- giving out heat and light- to bond with oxygen.
Magnesium will burn in air to from a metal-oxide, these are always basic.
They become non-metal oxides, which are, by nature, acids.
preparation (formation) of CO2
CaCO3 + 2HCl → CaCl2 + H2O + CO2
calcium carbonate + hydrochloric acid → calcium chloride + water + carbon dioxide
When metal carbonates are heated they become carbon dioxide and a metal.
For example: CuCO3 > CuO + CO2
copper carbonate > copper oxide + carbon dioxide
Properties of CO2
It is denser than air.
It is soluble in water at a high pressure.
Uses Of CO2
Carbon dioxide is dissolved into drinks at a high pressure, this makes CO2 bubbles in fizzy drinks.
Some fire extinguishers have CO2 in, because it is denser than air it will fall over the fire creating a barrier between the air and fire: the fire can't burn with out the oxygen in the air.
effect of CO2 on enviroment
Carbon dioxide prevents heat leaving the earth's atmosphere in rays that the earth emits.
Significant amounts of green house gasses will warm up the earth, changing the climate.
Hydrogen and Water
Combustion of Hydrogen
The combustion of hydrogen is its reaction with oxygen.
Water is created. and a lot of energy.
2H2 + O2 > 2H2O
Hdrochloric acid and metals
acid + metal > salt + hydrogen
For example: Mg + 2HCl > MgCl2 + H2
magnesium + hydrochloric acid > magnesium chloride + Hydrogen
test for water
anhydrous copper sulphate will become hydrous copper sulphate when it is reacted with water.
So if anhydrous copper sulphate goes from white to blue in the presence of a liquid it will be water.
If water is pure it will boil at exactly 100° and freeze at exactly 0°
Figuring out the reactivity series
reactions with water and acid
potassium, sodium, lithium and calcium all react with water and acids
magnesium, zinc and iron all react with acids (and very slowly with water.)
copper doesn't react with either.
The more vigorous the reaction the more reactive the metal.
The more things a metal will react with, the more reactive the metal.
A metal oxide or a metal salt dissolved in water
introduce a more reactive metal and it will displace the current one
introduce a less reactive metal and no displacement will take place
From this you can deduce which metals are more and less reactive.
The reducing agent is the more reactive metal which reduces the other metal.
The oxidising agent is the less reactive metal which allows the other metal to be oxidised.
Water and oxygen are needed to rust iron
iron that reacts with these becomes hydrated iron(iii) oxide.
Grease, oil, paint and plastic prevent air and/or water from coming into contact with iron.
This means the reaction that rusts iron can't occur.
Galvanising is coating in zinc.
This Zinc react in the air to form ZnCO3 which prevents air and/or water from coming into contact with the iron.
Sacrificial is covering a metal with a more reactive metal.
What this means is water and/or air will react with the more reactive metal instead of the one underneath.
Tests for ions and gasses
Cu2+, Fe2+ and Fe3+, using sodium hydroxide solution
Copper(ii) sulphate + sodium hydroxide > blue precipitate
Iron(ii) sulphate + sodium hydroxide > green precipitate
Iron(iii) sulphate + sodium hydroxide > brown precipitate
NH4+, using sodium hydroxide solution and identifying the ammonia evolved
NH4 + OH > NH3 + H2O
ammonium ions + hydroxide ions > ammonia + water
ammonia (pungent smelling gas) turns red litmus paper blue
Li+, Na+, K+, Ca2+ using flame tests
Sodium: orange (so strong can mask other colours)
Calcium: brick red
CO3 2-, using dilute hydrochloric acid and identifying the carbon dioxide evolved
Carbonate + acid > salt + water + carbon dioxide
Carbon dioxide produced will turn lime water cloudy
SO4 2- (sulphate ions) using dilute hydrochloric acid and barium chloride solution
SO4(2-) + HCl + Ba(2+) > white precipitate (barium sulphate)
Cl-, Br- and I-, using dilute nitric acid and silver nitrate solution
Chloride ions + nitric acid + silver nitrate > white precipitate (silver chloride)
Bromide ions + nitric acid + silver nitrate > cream precipitate (silver bromide)
Iodide ions + nitric acid + silver nitrate > yellow precipitate (silver iodide)
burns with a 'squeaky pop' sound
will relight a glowing splint
Turns lime water cloudy
Damp red litmus paper blue
Damp universal indicator purple
bleaches damp litmus paper white