Chemistry of the p-block
- Created by: holly_b
- Created on: 04-01-17 09:38
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- p-block
- Amphoteric Behaviour
- A substance which can acts as an acid and a base.
- p-block elements form amphoteric oxides and hydroxides.
- Lead Oxide
- As an acid
- PbO + 2NaOH + H2O --> Na2[Pb(OH)4]
- As a base
- PbO + 2HNO3 --> Pb(NO3)2 + H2O
- As an acid
- Lead Oxide
- Testing for amphoteric metals
- Solutions with amphoteric metals form precipitates when sodium hydroxide is added
- On adding excess sodium hydroxide the precipitate will redissolve.
- Solutions with amphoteric metals form precipitates when sodium hydroxide is added
- Stability
- The inert pair effect
- The lower valencies become more stable as the group (3, 4 and 5) is descended.
- Towards the bottom of the group there is an increasing tendancy for the s2 pair not to be used in the bonding.
- Ge(IV) is more stable than Ge(II).
- The inert pair effect
- Octet expansion
- The octet can be expanded by utilising the d-orbitals
- Examples
- PCl5
- SF6
- ClO4 -
- Examples
- The octet can be expanded by utilising the d-orbitals
- Al2Cl6
- The electron deficient aluminium uses a lone pair on the chlorine atom to form a coordinate bond.
- Other molecules can also form coordinate bonds to lose their electron deficiency.
- These are called donor-acceptor compounds where one molecule donates a lone pair and the other accepts it.
- Other molecules can also form coordinate bonds to lose their electron deficiency.
- The electron deficient aluminium uses a lone pair on the chlorine atom to form a coordinate bond.
- Boron Nitride
- Hexagonal boron nitride vs. graphite
- Similarities
- Forms hexagonal sheets.
- Differences
- Each boron has a nitrogen atom above and below it but in graphite atoms on adjoining layers are not directly above each other.
- BN does not have delocalised electrons so it is a good insulator.
- The B-N bond is polar.
- Similarities
- Cubic boron nitride
- Similarities
- Hard
- High melting point
- Uses
- Wear resistant coating
- Industrial abrasive
- Similarities
- Hexagonal boron nitride vs. graphite
- Oxidation states in group 4
- Carbon Monoxide
- Only stable compound to contain carbon in the +2 oxidation state.
- Acts as a reducing agent because its easily oxidised to +4.
- Carbon Dioxide
- Most stable carbon compound as carbon is in the +4 oxidation state.
- Acidic oxide which is soluble in water.
- This leads to the formation of carbonic acid.
- Lead(II) oxide
- PbO is the most stable oxide
- Amphoteric
- Lead(IV) oxide is the acts as an oxidising agent as it is easily reduced from +4 to +2.
- Carbon Monoxide
- Reactions of Cl2
- Water
- It forms chloric(I) acid (HOCl) and hydrochloric acid (HCl) in a reversible disproportionation reaction
- NaOH
- The equilibrium is shifted to the right
- The chlorate(I) ion is stable at room temperature.
- The equilibrium is shifted to the right
- Water
- Reactions of lead compounds
- NaOH
- White precipitate of Pb(OH)2 is formed
- NaOH
- White precipitate of Pb(OH)2 redissolves to form tetrahydroxyplumbate.
- HCl
- White precipitate of lead chloride is formed.
- KI
- Yellow precipitate of lead iodide is formed.
- NaOH
- Reactions of Chlorides
- Carbon and silicon chlorides are colourless liquids containing individual covalent molecules
- Stable chlorides = tetrachlorides
- CCl4 doesn't react with water as there are no available d-orbitals so there is no octet expansion.
- In silicon there are available d-orbitals so the water molecules can form coordinate bonds.
- Lead (II) chloride is insoluble in water.
- Sodium halide solids and concentrated sulfuric acid
- Chlorine
- Iodine
- Bromine
- Amphoteric Behaviour
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