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Chemistry > Transition elements > Flashcards

Transition elements Flashcards

1
Q

What are d-block elements?

A

They are metallic, have high melting and boiling points, and are shiny.
They conduct both heat and electricity, and their metallic properties give rise to some of their uses.

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2
Q

What are some of the uses of d-block elements?

A

Copper, silver, nickel and zinc have been used in coinage.
Iron is used in construction and tools.
Copper is used for electrical cables and water pipes.
Titanium is very strong and used in aerospace, and medicine - for joint replacements and cosmetic dentistry.

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3
Q

What is the electron configuration of chromium and copper?

A

Chromium - 1s2, 2s2, 2p6, 3s2, 3p6, 3d5, 4s1
Copper - 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1
This is because a half filled d5 sub shell and a fully filled d10 sub shell give additional stability to Cr and Cu.

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4
Q

What is the electron configuration of d-block ions?

A

When d-block elements (scandium to zinc) form positive ions, they lose their 4s electrons before any 3d electrons.
So, when forming an atom, the 4s orbital fills before the 3d orbitals.
Except for Cr and Cu.

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5
Q

What are transition elements?

A

D-block elements that form at least 1 ion with a partially filled d-orbital.
Sc and Zinc are d-block elements, but they are not transition elements.

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6
Q

Why is Scandium not a transition element?

A

Sc only forms the ion Sc3+ by losing two 4s electrons and a 3d electron.
Sc3+ is 1s2, 2s2, 2p6, 3s2, 3p6.
It has empty d-orbitals so it is not a transition element because it does not form ions with partially filled d-orbitals.

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7
Q

Why is Zinc not a transition element?

A

Zn only forms the Zn2+ ion by loss of two 4s electrons.
Zn2+ is 1s2, 2s2, 2p6, 3s2, 3p6, 3d10
It has a full d-sub shellso is not a transition element.

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8
Q

What are the properties of transition metals?

A

They form compounds in which the transition element has different oxidation states.
They form coloured compounds.
The elements and their compounds can act as catalysts.

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9
Q

What is the variable oxidation state property?

A

Transition elements form compounds with more than one oxidation state.
The number of oxidation states increases across the transition elements series to manganese, then decreases.
All transition elements form compounds with an oxidation number of +2.
A transition element in its highest oxidation state is often a strong oxidising agent.

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10
Q

What are the oxidation states and colours of transition elements?

A

Ti 3+ violet
V2+ violet, V3+ green, V4+ blue, V5+ yellow
Cr2+ blue, Cr3+ green, Cr6+ orange
Mn2+ light pink, Mn4+ light brown
Fe2+ pale green, Fe3+ pale yellow
Co2+ pink, Co3+ green
Ni2+ green
Cu2+ blue

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11
Q

How are transition metals heterogenous catalysts?

A

Haber process by solid iron catalyst:
N2(g) + 3H2(g) –> 2NH3(g)
Hydrogenation of veg fats into margarine by Nickel and H2
Decomposition using solid MnO2
2H2O2(aq) –> 2H2O (l) + O2(g)

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12
Q

How are transition metals homogenous catalysts?

A

Fe2+ ions catalyse peroxodiosulfate ions where everything is aqueous.

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13
Q

What is a complex ion?

A

A transition metal ion bonded to ligands by coordinate bonds.

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14
Q

What are ligands?

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.
A coordinate bond is a kind of covalent bond where one of the bonded atoms provides both of the electrons for the shared pair.
The coordinate number is the number of coordinate bonds attached to the central ion.

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15
Q

How are complex ions represented?

A

The complex ion is in square brackets with the overall charge on the outside.
e.g. [Cr(H2O)6]3+

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16
Q

What are monodentate ligands?

A

Donates one pair of electrons to the central metal ion.
H2O
NH3
Cl-
CN-
OH-

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17
Q

What are bidentate ligands?

A

Ligands that donate two pairs of electrons to the central metal ion to form two coordinate bonds.
1,2-diaminoethane (en) which forms [Co(en)3]3+
Ethanedioate ion (EDTA) (dicarboxylic acid with no H)

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18
Q

What are 6 coordinate complexes?

A

Coordination number of 6, forms an octahedral shape, with 90° bond angles.
[Mn(H2O)6]2+ formed from MnSO4 and H2O
[Co(H2NCH2CH2NH2)3]3+

19
Q

What are tetrahedral complexes?

A

Have four coordinate bonds, with bond angles of 109.5° around the central metal ion.
e.g. [CoCl4]2- which is blue.
[CuCl4]2- which is yellow.

20
Q

What are square planar complexes?

A

Occurs in complex ions of transition metals with 8 d-electrons in the d-sub shell - Pt2+, Pd2+ and Au3+.
e.g. [Pt(NH3)4]2+
There are 90° bond angles around the central metal ion.

21
Q

What is cis platin?

A

[Pt(NH3)2Cl2] forms a platinum complex inside a cell which binds to DNA and prevents DNA replication.
Activation of the cell’s repair mechanism eventually leads to apoptosis and tumour shrinkage.
But it has side effects such as kidney damage.

22
Q

What is cis-trans isomerism in square planar complexes?

A

[Pd(NH3)2Cl2]
In the cis isomer, the two identical groups are adjacent to each other, and are 90° apart.
In the trans isomer, the two identical groups are opposite (diagonal) each other, and are 180° apart.

23
Q

What is cis-trans isomerism in octahedral complexes?

A

For monodentate ligands with 4 of one ligand and 2 of the other, and also bidentate ligands, there are cis-trans isomers.
In the cis isomer, the 2 identical ligands are adjacent to each other and 90° apart.
In the trans isomer, the 2 identical ligands are opposite to each other and 180° apart.

24
Q

What is optical isomerism in octahedral complexes?

A

Occurs in octahedral complexes containing 2 or more bidentate ligands.
Optical isomers are non-superimposable mirror images of each other, and exists as the cis isomer.
[Co(en)2Cl2]+ has cis trans and optical isomerism.
[Ru(en)3]2+ has 3 bidentate ligands and only has optical isomerism.

25
Q

What is ligand subsitution?

A

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

26
Q

What is the reaction of Cu2+ with NH3?

A

[Cu(H2O)6]2+ + 4NH3 –> [Cu(NH3)4(H2O)2]2+ + 4H2O
pale blue to pale blue precipitate of Cu(OH)2 which dissolves in excess NH3 to dark blue.

27
Q

What is the reaction of Cu2+ with Cl-?

A

[Cu(H2O)6]2+ + 4Cl- –> [CuCl4]2- + 6H2O
pale blue solution to pale yellow solution
Cl- are larger in size so only 4 can fit around the central metal ion.

28
Q

What is the reaction of Cr3+ with NH3?

A

[Cr(H2O)6]3+ + 6NH3 –> [Cr(NH3)6]3+ + 6H2O
Violet to grey green precipitate of Cr(OH)3 which dissolves to purple.

29
Q

What is haemoglobin?

A

Haemoglobin contains 4 protein chains held by weak intermolecular forces.
Each chain has a haem molecule in its structure.
The central metal ion in a haem group is Fe2+.
Draw diagram [FeN5O=O], one N has a protein attached.

30
Q

What is haemoglobin and O2?

A

The Fe2+ in haemoglobin binds to O2 because of the increased pressure of oxygen in the capillaries in the lungs.
Oxyhaemoglobin is formed and releases oxygen when needed.
Haemoglobin also binds to CO2 and releases it from the red blood cells to be exhaled.

31
Q

What is ligand substitution of carbon monoxide and haemoglobin?

A

CO binds to Fe2+ in haemoglobin to form carboxyhaemoglobin, and a ligand substitution reaction happens that replaces O2 with CO.
CO binds more strongly than O2, and is irreversible.
If the concentration of carboxyhaemoglobin becomes too high, O2 transport is prevented, leading to death.

32
Q

What is the reaction of Cu2+ with NaOH?

A

Cu2+ + 2OH- –> Cu(OH)2 (s)
Blue solution forms a blue precipitate that is insoluble in excess NaOH

33
Q

What is the reaction of Fe2+ with NaOH?

A

Fe2+ + 2OH- –> Fe(OH)2 (s)
Pale green solution forms a dirty green precipitate that is insoluble in excess NaOH.
In air, forms orange-brown precipitate as is oxidised to Fe3+.
Fe(OH)2 –> Fe(OH)3

34
Q

What is the reaction of Fe3+ with NaOH?

A

Fe3+ + 3OH- –> Fe(OH)3 (s)
Pale yellow solution forms an orange brown precipitate that is insoluble in excess NaOH.

35
Q

What is the reaction of Mn2+ with NaOH?

A

Mn2+ + 2OH- –> Mn(OH)2 (s)
Pale pink solution forms a light brown precipitate which darkens on standing with air.
The precipitate is insoluble in excess NaOH.

36
Q

What is the reaction of Cr3+ with NaOH?

A

Cr3+ + 3OH- –> Cr(OH)3 (s)
Violet solution forms a grey green precipitate.
The precipitate dissolves in excess NaOH to form a dark green solution.
Cr(OH)3 + 3OH- –> [Cr(OH)6]3-

37
Q

What is the reaction of Fe2+, Fe3+ and Mn2+ ions with NH3?

A

React in the same way as with NaOH to form precipitates that do not dissolve.

38
Q

What is oxidation of Fe2+?

A

Fe2+ is oxidised to Fe3+.
MnO4- is reduced to Mn2+.
MnO4- is purple and is decolourised to form a colourless solution of Mn2+.
MnO4- + 8H+ + 5Fe2+ –> Mn2+ + 5Fe3+ + 4H2O

39
Q

What is reduction of Fe3+?

A

Fe3+ is reduced to Fe2+.
I- is oxidised to I2.
Orange brown Fe3+ to pale green Fe2+ ions.
I2 is brown, which is the overall colour of the reaction.

40
Q

What is reduction of Cr2O72-?

A

Cr2O72- + 14H+ + 3Zn –> 2Cr3+ + 7H2O + 3Zn2+
Orange to green
With excess Zn, Cr3+ is reduced to Cr2+ which is pale blue.
Zn + 2Cr3+ –> Zn2+ + 2Cr2+

41
Q

What is oxidation of Cr3+?

A

Hot alkaline H2O2 oxidises Cr3+ to CrO4-.
3H2O2 + 2Cr3+ + 10OH- –> 2CrO4- + 8H2O
Green to yellow

42
Q

What is reduction of Cu2+?

A

2Cu2+ + 4I- –> 2CuI + I2
Pale blue to white precipitate CuI and brown I2.
Cu2+ is reduced to Cu+.

43
Q

What is disproportionation of Cu+?

A

Cu2O (s) + hot H2SO4 –> Cu (s) + CuSO4 + H2O
Forms brown solid Cu and blue solution of CuSO4

Chemistry (26 decks)

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