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A-Level Chemistry > Transition elements > Flashcards

Transition elements Flashcards

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1
Q

What is a transition element?

A

d-block elements that form at least 1 ion with a partially filled d-orbital

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2
Q

What are the 2 d-block elements that are not transition elements?

A

Scandium and zinc

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3
Q

Why is scandium not a transition element?

A

Because it only forms an Sc 3+ ion - this has no d sub-shell

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4
Q

Why is zinc not a transition element?

A

It only forms a Zn 2+ ion and this has a fully d sub-shell so does not match the definition of a transition element

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5
Q

What are the properties of transition elements and their compounds?

A
  • They form compounds in which the transition element can have different oxidation states
  • They form coloured compounds
  • The elements and their compounds can act as catalysts
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6
Q

How many oxidation states does iron have?

A

2

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7
Q

What are the 2 oxidation states of iron and their colours?

A

+ 2 pale green
+ 3 yellow

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8
Q

How many oxidation states does chromium have?

A

3

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9
Q

What are the 3 oxidation states of chromium and their colours?

A

+2 blue
+3 green
+6 orange

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10
Q

What is a catalyst?

A

A substance that increases the rate of chemical reaction without itself changing

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11
Q

What catalyst does the Haber process use?

A

An iron catalyst

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12
Q

What catalyst does the decomposition of H2O2 use?

A

Manganese (IV) oxide, MnO2

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13
Q

What is a ligand?

A

A molecule or ion that donates a pair of electrons to a central metal ion to form a coordinate bond or dative covalent bond

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14
Q

What is a monodentate ligand?

A

A ligand that is able to donate one pair of electrons to a central metal ion

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15
Q

What is a didentate ligand?

A

A ligand that is able to donate 2 lone pairs of electrons to the central metal ion, forming 2 coordinate bonds

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16
Q

What are some monodentate ligand examples ?

A

H2O: (neutral charge)
:NH3 (neutral charge)
:Cl - (-1 charge)
:CN - (-1 charge)
:OH- (-1 charge)

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17
Q

What is a complex ion?

A

A metal ion surrounded by coordinately bonded ligands

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18
Q

What is coordination number?

A

The number of coordination bonds that are formed with the central metal atom/ ion

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19
Q

What is the shape of a 6-fold coordinate bond?

A

Octahedral

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20
Q

What are the possible shapes of a 4-fold coordination bond?

A

Tetrahedral or square planar

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21
Q

What complex ions can cis-trans isomerism occur in?

A

Square planar and octahedral

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22
Q

What is cis isomerism?

A

Where the groups are adjacent to one another (90 degrees)

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23
Q

What is trans isomerism?

A

Where the groups are opposite to one another (180 degrees)

24
Q

What complex ions can optical isomerism occur in?

A

Octahedral complexes containing 2 or more bidentate ligands

25
Q

What is an example of optical isomerism in complex ions?

A
26
Q

What is cis-platin?

A

A very effective drug used in many cancer treatments. It is the cis isomer of [PtCl2 (NH3)2]

27
Q

How is cis-platin thought to work?

A

It bind to the DNA in cancer cells and changes it - stopping them from reproducing them. Another theory is that it damages the cancer cells, killing them off. The exact mechanism of its working is unknown

28
Q

What does cis-platin look like?

A
29
Q

What is ligand subsitution?

A

A reaction in which one ligand on a complex is replaced by another ligand

30
Q

[Cu(H2O)6]2+(aq)+ 4NH3(aq) ⇌ [Cu(NH3)4(H2O)2]2+(aq) + 4H2O(l)

Colour change?

A

Pale blue to deep blue

31
Q

[Cu(H2O)6]2+(aq) + 2NH3(aq) ——> Cu(OH)2(H2O)4 + 2NH4+(aq)

Colour change?

A

Pale blue to a blue precipitate that is soluble in excess ammonia

32
Q

[Cu(H2O)6]2+(aq)+ 4Cl-(aq) ⇌ [CuCl4]2-(aq) + 6H2O(l)

Colour change?

A

Pale blue to yellow

33
Q

Is the complex ion more stable as [Cu(H2O)6]2+(aq) or [CuCl4]2-(aq)?

A

It is more stable if the shape changes to tetrahedral - [CuCl4]2-(aq)

It is changed because the Cl- ligands are larger than the H2O ones

34
Q

[Cr(H2O)6]3+(aq) + 3NH3(aq) ——> Cr(OH)3(H2O)3 + 3H2O(l)

Colour change?

A

Violet to grey-green precipitate thats soluble in excess NH3

35
Q

Cr(OH)3(H2O)3 + 6NH3(aq) ——> [Cr(NH3)6]3+(aq) + 3H2O(l) + 3OH¯(aq)

Colour change?

A

Violet to purple

36
Q

[Mn(H2O)6]2+(aq) + 2NH3(aq) ——> Mn(OH)2(H2O)4 + 2NH4+(aq)

Colour change?

A

Pale pink to off white, brown precipitate insoluble in excess NaOH

37
Q

[Fe(H2O)6]2+(aq) + 2OH¯(aq) ——> Fe(OH)2(H2O)4 + 2H2O(l)

Colour change?

A

Pale green to dirty green precipitate

38
Q

[Fe(H2O)6]3+(aq) + 3NH3(aq) ——> Fe(OH)3(H2O)3 + 3NH4+(aq)

Colour change?

A

Yellow to rusty-brown precipitate

39
Q

What do red blood cells contain?

A

Haemoglobin

40
Q

What is the purpose oh haemoglobin?

A

It carries oxygen around the body

41
Q

What are the 6 coordinates bonds to Fe 2+ in haemoglobin?

A

4 to nitrogen
1 to the protein globin
1 to the oxygen molecule

42
Q

About from oxygen, what can also bond to the Fe 2+ of haemoglobin?

A

CO. It binds more strongly and doesn’t get released; it binds to haemoglobin irreversibly. This leaves fewer functioning groups in the blood to carry oxygen around the body. So breathing in too much CO causes your blood to become very insufficient in the transport of oxygen - leading to death

43
Q

How does Cu 2+ react with NaOH and what is the colour change?

A
44
Q

How does Fe 2+ react with NaOH and what is the colour change?

A
45
Q

How does Fe 3+ react with NaOH and what is the colour change?

A
46
Q

How does Mn 2+ react with NaOH and what is the colour change?

A
47
Q

How does Cr 2+ react with NaOH and what is the colour change?

A
48
Q

How do Cu 2+ and Cr 3+ react with ammonia?

A

How they did in ligand substitution with ammonia

Cu (OH)2 —> [Cu(NH3)2(H2O)2]2+
Blue precipitate to deep blue solution
Cr (OH)3 —> [Cr(HN3)6]6+
Green precipitate to purple solution

49
Q

How do Fe 2+, Fe 3+ and Mn 2+ react with an excess of aqueous ammonia?

A

In the same way they reacted with sodium hydroxide

50
Q

How is Fe 2+ oxidised to Fe 3+ and what is the colour change?

A
51
Q

How is Fe 3+ reduced to Fe 2+ and what are the colour changes?

A
52
Q

How is Cr2O7 2- reduced to Cr 3+ and what is the colour change?

A
53
Q

How is Cr 3+ oxidised to CrO4 2-?

A
54
Q

How is Cu 2+ reduced Cu + and what is the colour change?

A
55
Q

What is the disproportionation reaction of Cu+ ions?

A

A-Level Chemistry (42 decks)

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