Chemistry 3.3 - P-Block Elements

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Elements in the p-block show two oxidation states...
Their maximum oxidation state matches the group number and their second oxidation state is two less, due to the 's' sub-shells.
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General trend for oxidation states?
As you move down the groups, higher oxidation states become less stable and lower oxidation states become more stable.
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Inert pair effect.
The tendency for heavier elements to form lower oxidation states.
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Why is it that heavier elements prefer to show lower oxidation states?
Their reluctant 's' electrons do not take part in chemical bonding.
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The 2nd period elements of the p-block only have access to 's' and 'p' orbitals. What does this mean?
These elements can have a maximum of 8 electrons in their outer shell, which limits the number of bonds that can be formed.
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Why does this not apply to period 3 elements and below?
They have access to d-orbitals and so can 'expand their octet': any electron in the outer shell can be used for bonding as there is no longer a limit of 8 electrons. This affects the number of bonds that can form.
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Summary: what is octet expansion?
The ability of some atoms to use their d-orbitals to have more than 8 electrons in their valence shell.
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PPQ: explain why P forms two chlorides, PCl3 and PCl5, whilst N only forms NCl3.
Phosphorus has access to 3d orbitals and so can expand its octet: one of its 's' electrons can be promoted and used for bonding. Nitrogen does not have access to d orbitals.
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Amphoteric
Possesses both acidic and basic properties.
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Many p-block elements form...
AMPHOTERIC OXIDES.
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Electron deficient atom
One that does not have a full outer shell.
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Dimer
Two molecules joined together.
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Why will aluminium chloride coordinate bond with another aluminium chloride molecule to form a dimer?
In aluminium chloride, the aluminium is electron deficient (6 electrons in its outer shell). Therefore, it will coordinate bond with a lone pair from the chlorine of another aluminium chloride to complete its outer shell and form a dimer
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Coordinate bond
A covalent bond in which both electrons come from the same atom.
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Covalent bond
Each atom supplies one electron to the bond.
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Structure of HEXAGONAL boron nitride?
SIMILAR TO GRAPHITE. Arranged in layers; atoms lie directly above and below one another; layers held together by vDW forces; no delocalised electrons; polar B-N bonds.
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Uses of hexagonal boron nitride?
Structural materials, e.g. electrodes, catalyst carriers in fuel cells, batteries.
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Structure of CUBIC boron nitride?
SIMILAR TO DIAMOND. Each boron is bonded to 4 nitrogen atoms; no delocalised electrons; high m.p. due to strong covalent bonds.
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Uses of cubic boron nitride?
Acts as wear-resistant coating and as an industrial abrasive.
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PPQ: describe the differences between graphite and BN in terms of bonding and structure.
All the atoms in graphite are the same; atoms in layers of BN lie directly above and below each other, but differ in graphite; BN bond is polar; delocalised electrons in graphite.
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Group 4 chemistry - common trend for the oxidation states?
As you move down the group, the +2 oxidation state becomes more stable and the +4 becomes less stable.
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Carbon monoxide is the only stable compound where carbon has an oxidation state of +2. Why is this compound a good reducing agent?
As the carbon will easily oxidise from +2 to +4.
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Lead (IV) oxide is the only stable compound where lead has an oxidation state of +4. Why is it a good oxidising agent?
As the lead will easily be reduced from +4 to +2.
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Can carbon tetrachloride react with water?
NO - it does not have access to d-orbitals, so it cannot expand its octet. It is limited to 8 electrons in its valence shell, and so no more covalent bonds can form.
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Can silicon tetrachloride react with water?
YES - it has access to 3d orbitals, alongside the 3s and 3p that are involved in the bonding to chlorine. So, lone pairs from the water molecules can coordinate bond with the vacant d-orbitals to form a complex molecule. 2 x HCl's are eliminated.
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Product of this reaction?
Silicon oxide and HCl.
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Can lead (II) chloride react with water?
NO - it is an ionic compound that does not dissolve in cold water.
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In general, metal oxides are classified as __1__ and non-metal oxides are classified as __2__?
1. Basic 2. Acidic
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Carbon dioxide is an acidic oxide. Give an example?
It dissolves in water to give a weakly acidic solution, AND it will react with a base (e.g. NaOH) to form a salt and water (e.g. sodium carbonate).
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What colour is lead (II) oxide?
It is an orange solid.
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Nature of lead (II) oxide?
Amphoteric.
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Are halogens oxidising agents or reducing agents?
Oxidising agents - they will accept an electron from another species and be reduced.
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As you move down group 7, do the halogens become stronger or weaker oxidising agents?
WEAKER - chlorine is the strongest oxidising agent (most easily reduced); iodine is the weakest.
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Which halogen is the strongest reducing agent?
Iodine (this also means it is most easily oxidised).
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Concentrated sulfuric acid: oxidising agent or reducing agent?
OXIDISING AGENT.
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What compound will always form when conc sulfuric acid reacts with a sodium halide?
A hydrogen halide. Depending on the halogen present, this can further be oxidised (this beomes easier as you move down the group as iodine is the most easily oxidised, as shown by its lower electrode potential value).
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The reaction between concentrated sulfuric acid and NaCl produces HCl gas. Will this be oxidised further?
NO - sulfuric acid is not a strong enough oxidising agent,.
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Observations?
Steamy fumes of HCl.
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The reaction between concentrated sulfuric acid and NaBr produces HBr gas. Will this be oxidised further?
Yes - the HBr is oxidised further to produce brown fumes of bromine, sulfur dioxide and water. Overall, this is a redox reaction as the bromine is oxidised whilst the sulphur is reduced.
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Observations?
Steamy fumes of HBr, brown fumes of bromine.
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The reaction between concentrated sulfuric acid and NaI produces HI gas. Will this be oxidised further?
Yes - the HI is oxidised further to produce purple fumes of iodine, sulphur dioxide and water. Overall, this is a redox reaction as the iodine is oxidised whilst the sulphur is reduced.
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Further reaction?
HI is a strong reducing agent, and so the sulfuric acid can be reduced to form solid sulpher and hydrogen sulphide.
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Observations?
Steamy fumes of HI, purple fumes of iodine, yellow solid (sulphur) and smell of rotten eggs (hydrogen sulphide).
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Disproportionation reaction
When an element ends up in two different compounds, one with a higher oxidation state and one with a lower oxidation state.
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Uses for chlorate I and II?
Both used in bleaches; chlorate I is used for the chlorination of bacteria as it can oxidise microbes.
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Other cards in this set

Card 2

Front

General trend for oxidation states?

Back

As you move down the groups, higher oxidation states become less stable and lower oxidation states become more stable.

Card 3

Front

Inert pair effect.

Back

Preview of the front of card 3

Card 4

Front

Why is it that heavier elements prefer to show lower oxidation states?

Back

Preview of the front of card 4

Card 5

Front

The 2nd period elements of the p-block only have access to 's' and 'p' orbitals. What does this mean?

Back

Preview of the front of card 5
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