p-block chemistry

This resource should hopefully cover all the basic knowledge needed fore the second topic in WJEC CH5. I hope it is useful. Good luck :)

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What does the term Amphoteric mean?
This is when a substance can react with both acids and bases.
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Reactions of lead and aluminium showing amphoteric behavior.
If you add sodium hydroxide to solutions of lead (II) nitrate or aluminium nitrate you will see a white precipitate that dissolves when more sodium hydroxide is added, giving a colouless solution.
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What is Octet expansion?
For compounds in group five and six, they need ten or twelve electrons in the outer shell to bond covalently. This if fine for the third period onwards as there is a d-orbital that we can expand into. This is called octet expansion.
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What is the inert pair effect?
As you move down the p block, the pair of electrons in the s-orbital become less likely to be involve in the bonding, these are called the inert pair. This makes the elements in the lower groups show an oxidation state 2 lower than would be expected.
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What is co-ordinate bonding?
This is when the shared pair of electrons come from the same atom.
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What is a dimer?
A species created when two molecules join together.
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What is meant by electron deficient?
When there are fewer than eight electrons in an atoms outer shell.
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What is a lone pair?
A pair of electrons in the outer shell, that are not involved in bonding.
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Aluminium chloride (AlCl3)
Aluminium chloride is electron deficient, this allows coordinate bonding to form between two aluminium chloride molecules forming a dimer.
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Tetrachloroaluminate (AlCl4-)
This is formed when aluminium chloride coordinate bonds with a chloride ion.
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What is a halogen carrier?
A species that can carry a halogen to react in a reaction. An example is Aluminium chloride (AlCl3), this molecule is used in the chlorination of benzene.
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Define Isoelectronic
This is when there are the same number of electrons in the outer shell. For example Boron Nitride is isoelectronic with carbon, and therefore has similar properties.
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Information on Hexagonal Boron Nitride
Similar structure to graphite. Hexagonal BN atoms lay above one another, where as they don't in graphite. Weak forces between layers so is a good lubricator. Hexagonal BN is used as an insulator, graphite is an electrical conductor.
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Information on Cubic Boron Nitride
Similar structure to diamond, with a tetrahedral shape. It is one of the hardest materials known with a very high melting temperature. Good heat conductor and is used for mounting high powered electronic components and supports for catalysts.
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Information on Boron Nitride Nanotubes
A layer of hexagonal boron nitride can be wrapped around carbon nanotubes, helps to act as an insulator.
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The inert pair effect on group 4 elements?
Lower elements have an oxidation of +2 compared to +4 on the elements higher up in the group. This is due to the inert pair effect.
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Carbon as a reducing agent
Carbon is stable in the +4 state, but in CO carbon has an oxidation state of +2.. It will therefore act as a reducing agent. It is useful in the extraction of metals from their oxides.
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Group 4 oxides and chlorides
In the top of group 4 the elements are non-metals and bond covalently and are gases or liquids. However at the bottom of group 4 you have Lead(II) oxide and chloride, these adopt giant ionic structures and are both solids.
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What is an acidic oxide?
An oxide that reacts with bases.
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What is a basic oxide?
An oxide that reacts with acids.
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Is carbon dioxide acidic or basic?
Acidic as CO2 reacts readily with bases.
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Chlorides + water
SiCl4 will react readily with water to produce SiO2 and gaseous HCl. CCl4 however doesn't react. The difference is that Si has a d-orbital that it can expand into whereas C doesn't.
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Pb2+ + OH-
White ppt. (Lead(II)hydroxide)
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Pb2+ + excess OH-
ppt. dissolves to form a colourless solution of Tetrahydroxoplumbate(II) [Pb(OH)4]2-
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Pb2+ + Cl-
White ppt of Lead(II) chloride
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Pb2+ + I-
Bright yellow ppt. of lead(II) iodide
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Define Disproportionation
A reaction where atoms of the same element become oxidized and reduced to form two different products.
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Order in oxidizing strength chlorine, bromine and iodine
[Most oxidizing] chlorine / Bromine / Iodine [Least oxidizing] (Chlorine has a more positive electrode potential than bromide, so will oxidize bromide to bromine)
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Reactions of chlorine with sodium chloride
If cold sodium chloride and sodium chlorate (I) NaOCl is formed. If heated sodium chloride and sodium chlorate(V) (NaClO3). Both of these reaction are example of disproportionation.
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Reaction equation for sodium halides and concentrated sulfuric acid?
NaX +H2SO4 -- NaHS)4 + HX
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Further reactions of HBr and HI
HBr can be further oxidized by the sulfuric acid to produce Br2 as orange fumes. HI can be further oxidized to form I2 which is a lack solid, or purple fumes.
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Uses of halogens and their compounds
Chlorine in water disinfection of water. Sodium chlorate (V) in weed killer. Polytetrafluoroethane (PTFE) in non stick for frying pans. Trichlorophenol (TCP) and iodine used as an antiseptic.
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Other cards in this set

Card 2

Front

Reactions of lead and aluminium showing amphoteric behavior.

Back

If you add sodium hydroxide to solutions of lead (II) nitrate or aluminium nitrate you will see a white precipitate that dissolves when more sodium hydroxide is added, giving a colouless solution.

Card 3

Front

What is Octet expansion?

Back

Preview of the front of card 3

Card 4

Front

What is the inert pair effect?

Back

Preview of the front of card 4

Card 5

Front

What is co-ordinate bonding?

Back

Preview of the front of card 5
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