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X A2 chemistry > Unit 5 transition metals > Flashcards

Unit 5 transition metals Flashcards

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1
Q

What is the d block of the periodic table?

A

The middle bit

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2
Q

What are the main transition metals to know about?

A

The ones on the row from titanium to copper

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3
Q

what is the exception to the rule that the 4s sub shell fills up before the 3d sub shell?

A

In copper and chromium.

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4
Q

What is the definition of a transition metal?

A

One that can form one or more stable ions with a partially filled d-subshell.

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5
Q

Why isn’t scandium a transition metal?

A

It only forms the sc 3+ ion. When is loses these 3 electrons it ends up with the electron configuration of argon.

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6
Q

Why is zinc not a transition metal?

A

It can only form the Zn2+ ion. When it does this it still has a completely full d shell.

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7
Q

When electrons are being removed from a transition metal, where do they come from first?

A

They come from the s shell and then the d shell.

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8
Q

What is the nature of the first ionsiation energies of the transition metals and what does this suggest?

A

They are all similar.

Suggesting all the electrons are coming from the same shell (4s)

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9
Q

What is the nature of the second ionsiation energies of the transition metals and what does this suggest?

A

They increase steadily with jumps at copper and chromium.

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10
Q

What is the nature of the third ionsiation energies of the transition metals and what does this suggest?

A

They increase as you go along but there is a fall at iron, then they start to go up again. From iron onwards the third electron removed is from the paired 3d subshell. Where there are two electrons in the same orbital they repel each other.

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11
Q

What is a complex ion?

A

A metal ion surrounded by dative covelent bonded ligands.

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12
Q

What is a ligand?

A

Atom,ion or molecule that donates a pair of electrons to a central metal ion.

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13
Q

What is the co-ordinate number?

A

The no. of dative covalent bonds that can form around the central metal ion. Usually 4 or 6 depending on the size of the ligand.

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14
Q

What is the shape of a complex ion with 6 ligands?

A

Octahedral.

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15
Q

What is the shape of a complex ion with 4 ligands?

A

Generally tetrahedral, but sometimes they form a square planar shape.

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16
Q

What is the shape of a complex ion with 2 ligands?

A

Straight linear shape.

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17
Q

What is the relationship between the charge of a complex ion and oxidation numbers?

A

Oxidation state of the metal ion= total oxidation state(charge of ion) - sum of the oxidation states of the ligands.

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18
Q

What is a monodentate ligand?

A

It has one pair of lone electrons

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19
Q

What is the name of a ligand with 2 pairs of electrons?

A

Bidentate.

e.g. ethane-1,2-diamine and ethanedioate

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20
Q

What is a polydentate?

A

A ligand with more than two pairs of electrons.

Like EDTA 4- which can form 6 bonds.

21
Q

What is haemoglobin?

A

a polydentate that has 4 nitrgoens to bond with fe 2+

22
Q

How do ligands cause colour?

A

Normally the 3d electrons of a transition element have the same energy
They are repelled by the electrons of the ligand to a higher energy but it isn’t the same amount for all electrons.
the 3d orbitals are split into 2 energy levels where electrons can jump.

23
Q

If a complex ion absorbs yellow light, what colour will it be?

A

Blue, the complement.

24
Q

What happens when ligands are exchanged?

A

Colour changes

25
Q

Comment on the stability of Cu 2+

A

Stable in aqueous solution.

Reduced to Cu metal be more electro positive metals. This is displacement

26
Q

Comment of the stability of Cu+

A

Unstable and disproportionates in aqueous solution

2Cu+ = Cu2+ and Cu

27
Q

What stabilises Cu+

A

Stable Ligands can (like Cl-)

28
Q

Why aren’t Cu- complexes coloured?

A

Full 3d subshell

But solid copper compounds can be coloured.

29
Q

What are the most common ions of chromium?

A

3+, 6+, 2+

in decreasing order of stability.

30
Q

What do Cr +6 ions form?

A

Chromate (CrO4)2- and dichromate (Cr2O7)2- ions.

Both are good oxidising agents as are easily reduced to Cr3+

31
Q

What are metal aqua ions?

A

a complex ion with a metal ion and water

32
Q

What happens when OH- ions are added to metal aqua ions?

A

An equilibrium is set up.
[M(H20)6]^3+ +H2O = [M(H2O)4(OH)2]^2+ + H3O+
Further equilibriums are set up and ultimately a insoluble metal hydroxide.

33
Q

How does water reactive with ammonia?

A

NH3 + H2O = NH4+ and OH-

34
Q

how does ammonia react with metal aqua ions ?

A

It reacts with water to give hydroxide ions so it is the same as sodium hydroxide. Add in excess and H2O and OH- ligands will be displaced by the NH3 and an soluble metal ion complex will form.

35
Q

what are the colour of copper ions?

A

with OH- blue particles
exces OH- nothing
Excess ammonia deep blue solution.

36
Q

what is the colour of Cr 3+

A

Violet when bonded to pure water impurities in the water, like Cl- make it green.

37
Q

colour of cr 2+ ions?

A

blue

38
Q

what is the colour of Cro4 2-?

A

yellow

39
Q

How does dichromate react with zinc?

A

reacts with zinc and H+ for water, zinc 2+ and Cr3+

zinc can further reduce Cr3+ to Cr2+ though the Cr2+ will oxide straight back in air.

40
Q

How do Cr3+ ions react with hydrogen peroxide in alkali solution?

A

it will be oxidised

will react with water and OH- for more water and CrO4 2-

41
Q

How would you turn dichromate to chromate or chromate to dichromate?

A

for the latter reaction add OH- and water is produced as well.
For the former add H+ and water is produced as well.

42
Q

what is chromium(II) ethanoate?

A

Cr2(CH3CO2)4(H2O)2

43
Q

How do you make chromium(II) ethanoate?

A

start with green chromium (III) chloride solution.
Reduce with zinc in acid to give blue Cr2+
Sodium ethanoate is added to give a red solution of chromium (II) ethanoate.

44
Q

what do you have to careful of when making chromium(II) ethanoate

A

It is very easily oxidised.
All of it has to happen in an inert atmosphere of nitrogen and oxygen has to be removed from all the liquids used by bubbling nitrogen through them.

45
Q

what are amphoteric substances?

A

they can react with acids and alkalis

e.g. chromium hydroxide Cr(H2O)(OH)3

46
Q

how does chromium hydroxide Cr(H2O)(OH)3 react with alkali?

A

Reacts with OH- to give water and [Cr(OH)6]3-

Zinc is the only other transition metal that can react in this way.

47
Q

how does chromium hydroxide Cr(H2O)(OH)3 react with acid?

A

reacts with H+ to give [Cr(OH)6]3-

all the other transition metals can act in this way.

48
Q

[Cr(OH)6]3- with an excess of ammonia?

A

a violet to a purple solution

[Cr(NH3)6)3+ and water.

X A2 chemistry (12 decks)

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