Chemistry Unit 3

Learn these trends:

as you go down the group the alkali metals become: 

Bigger atoms

More reactive

Higher density

Lower melting point

Lower boiling point

1) The alkali metals are very reactive.

2) They are: Lithium, Sodium, Potassium, Rubidium, Caesium.

3) The alkali metals all have ONE outer electron.

4) The alkali metals all form 1+ ions.

5) The alkali metals always form ionic compounds.

6) Reaction with water produces Hydrogen gas.

2Na (s) + 2H2O(l) --> 2NaOH (aq) + H2(g)

2K(s) + 2H2O(l) --> 2KOH (aq)  + H2

Transition Elements:

1) Are good conductors of heat and electricity.

2) They're very dense, strong and shiny.

3) Transition metals are much less reactive than group 1 metals - they don't react very much with water or oxygen, for example.

4) They're also much denser, stronger and harder than the group 1 metals, and have much higher melting points (except for mercury, which is liquid at room temperature). E.g. iron melts a 1500oC, copper at 1100oC and zinc and 400oC.

Transition metals often have more than one ion, e.g. Fe2+, Fe3+.

Two other examples are copper: Cu+ and Cu2+ and chromium: Cr2+, Cr3+ and Cr6+. The different ions usually form different-coloured compounds too: Fe2+ ions usually give green compounds, whereas Fe3+ ions usually form red/brown compounds e.g. rust.

The compounds are very colourful.

1) The compounds are colourful due to the transition metal ion they contain, e.g. potassium chlomate(VI) is yellow. Potassium maganate(VII) is purple. Copper(II) sulphate is blue. 

2) The colour of people's hair and also the colours in gemstones, like blue samphires and green emeralds, and the colours in pottery glazes are all due to transition metals. And weathered copper is a lovely  colourful green. 

Transition metals and their compounds all make good catalysts.

1) Iron is the catalyst used in the Haber process for making ammonia. 2) Maganese(IV) oxide is a good catalyst for the decomposition of hydrogen peroxide. 3) Nickel is useful for turning oils into fats for making margarine.

Their properties are dues to the way their electron shells fill.

1) In an atom, as you get further from the nucleus, energy levels get closer together until they start to overlap.This first happens between energy levels 3 & 4.It affects the way the electron shells fill.

2) Potassium has 19 electrons - but the 19th electron goes into the 4th energy level, not the 3rd. The electron arrangements 2,8,8,1. Same thing with the next element, Calcium - which is 2,8,8,2.

3) The next ten elements (the transition metals) put their electrons into the overlapping 3rd energy level until its full.

Titrations are used to find out concentrations.

1) Titrations allow you to find out exactly how much acid is needed to neutralise a quantity of alkali or alkali for acid.

2) You put some alkali in a flask , along with some indicator. The indicator used depends on the strengths of the acid and alkali.

3) Add the acid, a bit at a time, to the alkali using a burette - giving the flask a regular swirl. Go especially slowly (a drop at a time) when you think the alkali is almost neutralised. 

4) The indicator changes colour when all the alkali has been neutralised, e.g. phenolphthalein is pink in alkalis, but colourless in acids.

5) Record the amount of acid used to neutralise the alkali. It's best to repeat this process a few times, making sure you get (pretty much) the same answer each time.