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AS/A2 CHEMISTRY > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

What is special about d block elements electron configurations?

A

It will have at least one s electron and at least one d electron but no p electrons in its outer shell.

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2
Q

Why is Cr configuration 4s13d5?

A

The repulsion between 2 paired electrons in the 4s orbital is more than the energy difference between 4s and 3d subshells.

Therefore it is more stable to have unpaired electrons in the higher energy 3d orbital than paired electrons in the lower 4s orbital.

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3
Q

What is common of all ions of the d block elements?

A

1) 3d subshell is lower in energy than the 4s subshell

2) 4s electrons are always removed first

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4
Q

What is the definition of a transition metal?

A

A metal which forms at least 1 stable ion with partially filled d orbitals

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5
Q

Which d block elements are not transition metals?

A

Zn and Sc, they are only able to form 1 oxidation state

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6
Q

What is the definition of a complex ion?

A

An ion comprising one or more ligands attached to a central metal cation via dative covalent bonds

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7
Q

What is the definition of a ligand?

A

A species which can use its lone pair of electrons to for a dative covalent bond with a transition metal.

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8
Q

What are some common ligands?

A

H2O, NH3, Cl-, OH-, CN-

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9
Q

What features must cations in complex ions have?

A

1) Orbitals with low energy
Empty orbitals of low energy
Electrons from ligands can be accepted if empty
2) High charge density
Able to strongly attract electrons from ligands
3) Size is small of cation

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10
Q

What is the definition of the co-ordination numbers?

A

The number of lone pairs of electrons which a cation can accept

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11
Q

What governs the co-ordination number of the cation?

A

1) Size of the cation
2) Size of the ligands
3) Charge of the ligands
4) Electron configuration

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12
Q

How are complex ions in the solid state written?

A

Compound.Ligands eg FeSO4.6H2O(s)

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13
Q

What else can a “dot.” represent?

A

A water molecule of crystallisation i.e. where the water is not acting as a ligand but a link between ions

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14
Q

Name some common examples of octahedral complexes?

A

1) [Cu(H20)6]2+
2) [Fe(H2O)6]2+
3) [Cr(NH3)6]3+

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15
Q

Name some common examples of tetrahedral complexes?

A

1) [Co(Cl4)2-]

2) [Cu(Cl4)2-]

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16
Q

Name some common examples of square planar complexes?

A

[(NH3)2Pt(Cl2)] can show EZ isomerism

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17
Q

Name some common examples of linear complexes?

A

1) [Ag(NH3)2]+
2) [Ag(Cl2)]2-
3) [Ag(CN20]-

18
Q

Why can square planar complexes show EZ isomerism?

A

Restricted rotations

19
Q

What do the ligands have to be in square planar complexes to show EZ isomerism?

A

Not all identical

20
Q

What kind of isomerism can octahedral complexes display?

A

EZ isomerism (4 ligands of one type and 2 ligands of a different type)

21
Q

What other kinds of isomerism can octahedral complexes display?

A

Optical isomerism

22
Q

What criteria must octahedral complexes meet before they can display optical isomerism?

A

1) 3 bidentate ligands
2) 2 bidentate + 2 monodentate ligands
3) Hexadentate ligands

23
Q

What is the effect of a ligand on the polarising power of the metal cation?

A

Reduces the polarising power by increasing the size

24
Q

Which needs more heat to break the molecule, a complex ion or water of crystallisation products?

A

The complex ions

25
Q

Why do transition metals form different colours?

A

Incoming ligands repel the electrons in the transition metal atom and so they are raised in energy. The resulting light is therefore missing certain frequencies and is coloured.

26
Q

How are the d orbitals split when electrons on the transition metal are raised in energy?

A

3 orbitals in lower energy than the other 2

27
Q

What 2 criteria must be satisfied if the ion is to be coloured?

A

1) There must be splitting of the d orbitals which only happens in the presence of ligands
2) the d orbitals must be partially filled

28
Q

What governs the colour of a complex ion?

A

1) The ligand
2) The coordination number
3) The oxidation state

29
Q

What are the first and second steps of making haemoglobin?

A

1) Fe2+ + porphyran (tetradentate ligand)= haem

2) Haem + globin + oxygen = oxyhaemoglobin

30
Q

Why is carbon monoxide dangerous?

A

It is a similar size and shape to oxygen and forms a much stronger bond with Fe2+

31
Q

What is the test for aldehydes?

A

Tollen’s reagent- active reagent is reduced to silver by the aldehyde and reducing sugars

32
Q

How is AgBr removed from a photographic film?

A

Addition of sodium thiosuplhate

33
Q

How are complex ions used in electroplating?

A

Cyanide ions form stable complex with silver and gold which allows it to be extracted from naturally occurring structures.

34
Q

Why can transition metals act as catalyst?

A

Their ability to form more than one oxidation state

35
Q

How does a catalyst work?

A

1) Alters the rate of reaction
2) Remains chemically unchanged
3) Lowers the activation energy by providing an alternative pathway

36
Q

What is a homogeneous catalyst?

A

It is a catalyst in the same state as the reactants

It involves aqueous transition metals, catalysing the reaction

37
Q

what is a heterogeneous catalyst?

A

It is a catalyst which allows the reactant molecules to bond to the surface of the metal usually by attracting surface electrons.

38
Q

What is the difference between adsorption and chemisorption

A

Adsorption- the reactants and metal are bonded by intermolecular forces
Chemisorption- metal and reactants form a covalent bond

39
Q

What is the trend in adsorption across the d block?

A

Decreases from left to right

40
Q

What happens to Fe2+ in aqueous solution?

A

Readily oxidised to Fe3+

41
Q

What happens to Mn (+7) in acidic solution?

A

Reduced to Mn2+

AS/A2 CHEMISTRY (17 decks)

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