5.3.1 - Transition Elements Flashcards

1
Q

What is a transition element?

A

A d-block element that has at least one stable ion with an incomplete d subshell.

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2
Q

What are the exceptions when doing electron configuration?

A

Chromium and copper.

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3
Q

What is the electron configuration of chromium?

A

[Ar]3d5 4s1

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4
Q

What is the electron configuration of copper?

A

[Ar] 3d10 4s1

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5
Q

Why is the electron configuration different for copper and chromium?

A

The 4s subshell and 3d subshell are very close in energy. Therefore there is only one electron in the 4s subshell. This reduces electron repulsions and gives chromium extra stability from a half filled 3d subshell and copper extra stability from a full 3d subshell.

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6
Q

Where are electrons lost from when forming ions?

A

Lost from the 4s first, then the 3d.

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7
Q

Why are ions formed this way?

A

The 3d and 4s subshells are close in energy and once they are occupied, repulsion between the electrons causes the 4s subshell to have a higher energy than the 3d.

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8
Q

Why are scandium and zinc not transition elements?

A

They form ions without an incomplete subshell.

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9
Q

What are the properties of transition metals?

A

They exist in more than one oxidation state. They form coloured solutions when dissolved in water, they frequently catalyse chemical reactions.

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10
Q

Fe2+

A

Green

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11
Q

Fe3+

A

Brown

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12
Q

Mn2+

A

Pale pink

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13
Q

Mn7+

A

Purple

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14
Q

Cu2+

A

Blue

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15
Q

Cr2+

A

Blue

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16
Q

Cr3+

A

Green

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17
Q

Cr6+

A

Orange

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18
Q

Ni2+

A

Green

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19
Q

Examples of when transition metals catalyse reactions?

A

Iron in the Haber process, nickel in hydrogenation of C=C bonds, vanadium (V) oxide in the contact process.

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20
Q

Complex ion?

A

A central transition metal ion bonded to one or more ligands by coordinate bonds.

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21
Q

Ligand?

A

An ion or molecule with a lone pair of electrons that can be donated to a transition metal to form a coordinate bond.

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22
Q

Coordinate number?

A

The total number of coordinate bonds between a central metal ion and its ligand.

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23
Q

Monodentate ligand?

A

A ligand that donates one pair of electrons to the central metal ion.

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24
Q

Water as a monodentate ligand?

A

:OH2 no charge

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25
Ammonia as a monodentate ligand?
:NH3 no charge
26
Thiocynate as a monodentate ligand?
:SCN- -1
27
Cyanide as a monodentate ligand?
:CN- -1
28
Chloride as a monodentate ligand?
:Cl- -1
29
Hydroxide as a monodentate ligand?
:OH- -1
30
What is a bidentate ligand?
One that donates two pairs of electrons to the central transition metal ion forming 2 coordinate bonds.
31
What is the name and bond angle of a complex ions with 6 coordinate bonds?
Octahedral 90 degrees.
32
What is the name and bond angle of a complex ion with 4 coordinate bonds?
Tetrahedral 109.5, square planar 90 degrees.
33
Which complex ions are usually square planar?
Nickel, palladium and platinum.
34
What is stereoisomerism?
Same molecular and structural formula, but different arrangement of atoms in space.
35
What are the bond angles in cis and trans?
Cis - 90, trans 180
36
What is optical isomerism?
When there is a different arrangement of the ligands in space which gives non-superimposable mirror images that rotate plane polarised by equal amounts in opposite directions.
37
What is cis Platin and what is it used for?
The cis isomer of platin. It is used as an anti cancer drug which binds to DNA in cancer cells and prevents cell division.
38
What is formed when any copper salt is dissolved in water?
The hexaaquo complex [Cu(H2O)6]2+
39
Write the equation for the reaction between chloride ions and the hexaaquo complex of copper.
[Cu(H20)6]2+ + 4Cl (reversible sign) [CuCl4]2- + 6H20
40
What colour is [Cu(H2O)6]2+
Blue solution
41
What colour is [CuCl4]2-
Yellow solution
42
Write the equation for the reaction between the hexaaquo complex of copper and ammonia.
[Cu(H2O)6]2+ + 4NH3 -> [Cu(NH3)4 (H2O)2]2+ + 4H2O
43
What is the colour of [Cu(NH3)4 (H2O)2]2+ and what is interesting about its shape?
Deep blue solution. Distorted octahedral shape due to longer H2O bonds.
44
What happens when ammonia solution is added dropwise to [Cu(H2O)6]2+
A pale blue precipitate of copper hydroxide is formed first which then dissolved in excess ammonia to form a deep blue solution. The ammonia is able to act as a base (removing a proton from the water) and a ligand (using its lone pair)
45
What is the hexaaquo complex of chromium?
[Cr(H2O)6]3+
46
What is the equation for when the hexaaquo complex of chromium is added to ammonia?
[Cr(H2O)6]3+ + 6NH3 -> [Cr(NH3)6]3+ + 6H2O
47
What colour is [Cr(H2O)6]3+
Green solution is sulphate ions present, violet if not.
48
What colour is [Cr(NH3)6]3+
Purple solution.
49
What happens when ammonia solution is added dropwise to the hexaaquo complex of chromium?
A grey green precipitate of chromium hydroxide is formed first which then dissolves in excess ammonia to form a purple solution.
50
What happens to Cu2+ when NaOH is added?
Blue precipitate.
51
What happens when NH3 is added to Cu2+?
Blue precipitate
52
What happens when excess NH3 is added to Cu2+?
Dissolves to deep blue solution.
53
What happens when NaOH is added to Fe2+?
Green precipitate which oxides to orange/brown.
54
What happens when NH3 is added to Fe2+?
Green precipitate which turns rusty brown due to oxidation.
55
What happens when NaOH is added to Fe3+?
Rusty brown precipitate.
56
What happens when NH3 is added to Fe3+?
Rusty brown precipitate
57
What happens to Mn2+ when NaOH is added?
Light brown precipitate which turns dark brown due to oxidation.
58
What happens to Mn2+ when NH3 is added?
Light brown precipitate which turns dark brown due to oxidation.
59
What happens when NaOH is added to Cr3+?
Green precipitate
60
What happens when XS NaOH is added to Cr3+?
The precipitate dissolves back to a green solution.
61
What happens when NH3 is added to Cr3+?
Green precipitate
62
What happens when XS NH3 is added to Cr3+?
Precipitate dissolves to green solution.
63
What is the half equation of Cu2+ reaction with NaOH?
Cu2+ + 2OH- -> Cu(OH)2
64
What is the half equation for Fe3+ reacting with NaOH?
Fe3+ + 3OH- -> Fe(OH)3
65
MnO4-
Purple
66
I-
Colourless
67
I2
Red brown
68
Cr2O7-
Orange
69
Zn
Grey solid
70
Zn2+
Colourless
71
H2O2
Colourless
72
O2
Gas
73
H2O
Colourless
74
What is equation for the reduction of Cu by I-?
2Cu+ + 4I- -> 2CuI + I2
75
What is CuI
White precipitate
76
What is I2 aqueous
Red brown solution
77
What is the equation for the disproportionation of Cu?
2Cu+ -> Cu + Cu2+
78
What does haemoglobin contain?
Fe2+ ions which form 6 coordinate bonds. Four of the lone pairs come from nitrogen atoms, and the fifth comes from a nitrogen atom on a protein (globin)
79
What happens in the lungs with haemoglobin?
The oxygen concentration is high so the water ligand is substituted for an oxygen molecule forming oxyhemoglobin.
80
What happens if carbon monoxide is inhaled?
The haemoglobin swaps its water ligand for a carbon monoxide ligand forming carboxyhaemoglobin.
81
Why is it bad when carboxyhaemoglobin is formed?
The CO is a strong ligand and doesn’t readily exchange with oxygen or water ligands, meaning the haemoglobin cannot transport oxygen anymore.