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Chemisty A level > Transition elements > Flashcards

Transition elements Flashcards

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1
Q

What is a transition element?

A

an element that forms one of more stable ions with a partially filled d sub-shell

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2
Q

How many electrons can a d sub-shell hold?

A

10

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3
Q

Which 2 elements in period 4 of the transition elements are not actually transition elements?

A

zinc and scandium

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4
Q

Why is zinc not a transition element?

A

is only forms Zn2+ by the loss of two 4s electrons which gives the configuration 3p6 3d10 - so its ion has a fully filled 3d subshell

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5
Q

Why is scandium not a transition element?

A

Sc only forms Sc3+ as a stable ion by loosing two 4s electrons which gives the configuration 3s2 3p6 so it has an empy 3d sub-shell

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6
Q

Which orbital fills up first when forming an atom of a transition element?

A

4s orbital

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7
Q

Which orbital empties first when forming an ion of a transition element?

A

4s

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8
Q

What are the 2 exceptions to the 4s orbital filling up first?

A

Copper and Chromium

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9
Q

What is the electron configuration of chromium? (3d and 4s)

A

3d 5, 4s 1

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10
Q

What is the electron configuration of copper (3d and 4s) ?

A

3d 10, 4s 1

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11
Q

What are the 3 properties of transition metals?

A
  1. variable oxidation states in compounds
  2. metals and compounds can act as catalysts
  3. they form coloured compounds
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12
Q

Why can transition metals form variable oxidation states?

A

the energies of 4s and 3d electrons are very similar, these elements can lose various number of electrons when they form stable compounds

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13
Q

How does a catalyst work?

A

provides an alternative pathway for a reaction with a lower activation energy thereby speeding up the reaction

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14
Q

What 2 reactions does iron catalyse?

A

the haber process
N2 + 3 H2 == 2NH3

acts as a halogen carrier in electrophilic substitutions

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15
Q

What reaction does vanadium (V) oxide (V2O5) catalyse?

A

the contact process
2 SO2 + O2 == 2 SO3

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16
Q

What reaction is catalysed by Ni?

A

hydrogenation of alkenes

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17
Q

What reaction does Pt catalyse?

A

hydrogenation of nitriles

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18
Q

What reaction does manganese (IV) oxide (MnO2) catalyse?

A

decomposition of hydrogen peroxide
2 H2O2 —> 2 H2 + O2

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19
Q

What are catalysis by transition metals important for?

A

industrial processes

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20
Q

Why are catalysts important in industrial processes?

A
  • they reduce energy usage so reactions can take place at lower temps
  • allow alternative reactions to be used which would be to slow to take place under reasonable conditions
  • may have better percentage yield or atom economy
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21
Q

Why do transition metals form coloured compounds?

A

they have a patially filled d subshell

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22
Q

What is a complex ion?

A

a central transition metal ion is surrounded by ligands bonded by dative covalent bonds

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23
Q

What is a ligand?

A

an ion or molecule that donates a lone pair of electrons to a central metal ion by forming a dative covalent bond

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24
Q

What is a hexaaqua ion?

A

a complex ion containing 6 water molecules

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25
What is a monodentate ligand?
ligand that forms 1 dative covalent bond to the same metal ions
26
What is a bidentate ligand?
it has 2 lone pairs so it is able to form 2 dative bonds with the same metal ion
27
What is the co-ordination number?
the number of coordinate bonds formed by the ligands to the metal ion in a complex ion
28
What are the 2 most common coordination numbers?
4 or 6
29
What 2 shapes can a complex ion with a coordination no. of 4 form?
tetrahedral or square planar
30
What is the bond angle of square planar?
between 90 degress and 180 degrees
31
What are the 2 examples of bidentate ligands?
ethandioate ethane - 1,2 - diamaine
32
How do you find the overall charge on a complex ion?
the sum of the charges on the metal ion and the ligands present
33
What shape does a complex ion with a coordination no of 6 form?
octrahedral
34
What bond angles does octrahedral shape have?
between 90 degrees and 180 degrees
35
What are the 3 elements square planar shape forms ?
platinum (II) palladium (II) Gold (III)
36
What isomerism can octrahedral complex ions show?
cis-trans and opitcal
37
What isomerism can square planar complex ions form?
cis-trans
38
What isomerism does tertahedral complex ions show?
opitcal
39
What is cis-platin?
the cis isomer of [Pt(NH3)2Cl2]
40
What is the use of cis-platin?
cancer treatment
41
How is cis-platin used in cancer treatment?
It binds to DNA of cancer cells preventing replication and so the cancer cells cannot divide
42
What is ligand substitution?
one ligand replacing another
43
What are the 2 reasons that ligand substitution occurs?
1. another ligand is capable of forming stronger coordinate bonds to the metal ions, replaces a ligand with weaker coordinate bonds 2. a ligand is added at a high conc may replace another ligand present at a lower conc
44
What are the 3 ligand substitution reactions you need to know?
1. addition of conc HCl (aq) copper (II) ions 2. addition of (aq) ammonia to (aq) Copper (II) ions 3. addition of (aq) ammonia to (aq) chromium (III) ions
45
What are the colour changes in the addition of conc HCl to copper (II) ions?
blue solution --> green --> yellow
46
What is the colour change when (aq) NH3 is added to Cu2+ ions?
blue --> deep blue solution
47
What is the colour change when (aq) NH3 is added to Cr3+ ions?
violet ---> purple
48
How is heamoglobin able to carry oxygen in terms of ligand substitution?
a molecule of )2 can reversibly replace a water ligand around the Fe2+ ion by ligand substiution
49
Why does CO bind to heamoglobin better than O2?
CO is a better ligand as it can form stronger coordinate bonds to Fe2+
50
What are the 5 reactions with NaOH that you need to know?
Cr3+ Mn2+ Fe2+ Fe3+ Cu2+
51
What is the colour change for the reaction of Cr3+ and NaOH?
violet --> dark green precipitate
52
What is the colour change for the reaction of Mn2+ and NaOH?
pale pink ---> light brown precipitate
53
What is the colour change for the reaction of Fe2+ and NaOH?
pale green ---> green precipitate
54
What is the colour change for the reaction of Fe3+ and NaOH?
yellow ---> orange-brown precipitate
55
What is the colour change for the reaction of Cu2+ and NaOH?
blue ----> blue precipitate
56
What is the only TM hydroxide that will redissolve in excess NaOH?
Cr(OH)3
57
What is the colour change of adding excess NaOH to Cr(OH)3?
green solid ---> dark green solution
58
How does (aq) NH3 react with TM ions?
it is a weak base so it (aq) solution it contains OH- ions these OH- ions react with 2+ and 3+ TM ions in the same was as they would react with NaOH
59
What 2 TM hydroxides will redissolve when excess NH3 is added?
Cu(OH)2 Cr(OH)3
60
Why does Cr3+ ions sometimes appear green not violet?
it can appear green due to their being impurities but it is violet when pure
61
What is the colour change when excess NH3 is added to Cu(OH)2?
blue solid ---> deep blue solution
62
What is the colour change when excess NH3 is added to Cr(OH)3?
grey-green solid ----> purple solution
63
Why does reacting NaOH with Fe2+ actually appear brown not green?
Fe2+ is oxidised by the air to form Fe3+ which forms an orange-brown precipitate when reacting with NaOH
64
What colour is iodine?
brown
65
How is Cu2+ reduced to Cu+?
using Iodine
66
What is observed when Cu2+ is reduced to Cu+ by iodine? (colour changes)
blue solution ---> white solid and brown solution
67
What happens to Cu+ in (aq) solutions? (+ equation)
it is unstable so it disproportionates: 2Cu+ ----> Cu2+ + Cu (s)
68
What colour is Cu solid?
reddish brown = rust
69
How is Cr3+ oxidised to form CrO4 (2-) ?
by hydrogen peroxide under alkaline conditions
70
What is the colour change of oxidising Cr3+ to CrO4 (2-) ?
violet or green ----> yellow
71
How can CrO4 (2-) be converted to Cr2O7 (2-)?
adding (aq) acid to CrO4 (2-)
72
What is the colour change of converting CrO4 (2-) into Cr2O7 (2-)?
yellow ----> orange
73
How is Cr2O7 (2-) reduced to Cr3+?
adding Zn under acidic conds
74
What is the colour change of reducing CrO7 (2-) into Cr3+?
orange ---> green
75
What coulour is [Cu(H2O)6] 2+ ?
pale blue solution
76
What colour is Cu(OH2) (s) ?
pale blue precipitate
77
What colour is [Cu(NH3)4 (H2O)2] 2+ ?
dark blue solution
78
What colour is CuCl4 - ?
yellow solution
79
What colour is CuI and I2?
CuI - white precipitate I2 - brown solution
80
What colour is Cu2+?
blue solution
81
What colour is CoCl4 - ?
blue
82
What colour is [Cr(H2O)6] 3+ ?
violet (green with impurities)
83
What colour is Cr(OH)3 (s) ?
dark green precipitate
84
What colour is [Cr(NH3)6] 3+?
purple
85
What colour is Cr2O7 (2-) ?
orange
86
What colour is CrO4 (2-) ?
yellow
87
What colour is [Mn(H2O)6] 2+?
pale pink solution
88
What colour is Mn(OH)2 (s) ?
pale brown precipitate
89
What colour is [Fe(H2O)6] 2+?
pale green
90
What colour is Fe(OH)2 (s)?
dark green precipitate
91
What colour is [Fe(H2O)6] 3+ ?
yellow
92
What colour is Fe(OH)3 (s)?
orange-brown precipitate
93
What colour is MnO4 - ?
purple
94
What is the colour change of reducing Fe3+ to Fe2+ with I- ions?
orange brown (Fe3+) --> brown (iodine)
95
What complex ions is a green-grey precipitate?
[Cr(OH)2 (H2O)4]
96
Why is Cu+ a white precipitate?
it has a full d-subshell
97
What colour is [Co(H2O)6] 2+?
pink
98
What is the use of [Co(H2O)6] 2+?
used as a water detecter, add Cl- ions and heat, it will turn blue to form [CoCl4] 2- when water has been removed
99
What is the equation when excess NH3 is added to Cu(OH)2?
Cu(OH)2 (s) + 4 NH3 (aq) + 2 H2O (l) --> [Cu(NH3)4 (H2O)2] 2+ (aq) + 2 OH- (aq)
100
What is the equation when excess NH3 is added to Cr(OH)3?
Cr(OH)3 (s) + 6 NH3 (aq) --> [Cr(NH3)6] 3+ (aq) + 3 OH- (aq)
101
What is the equation of the reduction of Fe3+ by I- ions?
2 Fe3+ + 2 I- ---> 2 Fe2+ + I2
102
What colour is Cr2+?
blue

Chemisty A level (39 decks)

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