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Chemistry, Module 5 OCR > 5.3.1 Transition elements > Flashcards

5.3.1 Transition elements Flashcards

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1
Q

Definition of a transition element?

A

A d-block element that forms at least one ion with a partially filled d-subshell.

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2
Q

Properties of a transition element. (7)

A

Contains metallic bonding: high melting and boiling points.

Hard

Shiny

High density

Forms coloured compounds

Has different oxidation stages when in a compound.

Their elements and compounds can act as catalysts.

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3
Q

Why is scandium not a transition element?

A

Sc only forms one ion: Sc3+

This ion has no electrons in the d- subshell.

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4
Q

Why is Zinc not a transition element?

A

Only forms one ion: Zn2+

Since the 4S sub-shell empties before the 3d sub-shell, the 3d sub-shell is filled.

Fully filled d-sub shell, therefore cannot be a transition element.

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5
Q

What is the electronic configuration of Chromium and why is it like this?

A

[Ar] 4s^1 3d^5

The 3d sub-shell prefers having a half occupied/ fully occupied sub- shell due to spin pair repulsion/ stability.

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6
Q

What is the electronic configuration of Copper and why is it like this?

A

[Ar] 4s^1 3d^10

The 3d sub-shell prefers having a fully occupied sub- shell due to stability so an electron is removed from the 4s sub-shell.

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7
Q

What is a complex ion?

A

Central metal ion surrounded by ligands.

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8
Q

What is a ligand?

A

Molecule/ ion that donates a pair of electrons to metal ion to form a dative covalent bond/ co-ordinate bond.

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9
Q

What are the coloured compounds of Fe2+ and Fe3+

A

Fe2+: pale green

Fe3+: yellow

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10
Q

What are the coloured compounds of Cr3+ and Cr6+

A

Cr3+: green

Cr6+: yellow/ orange

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11
Q

Give four examples of how transition metals act as heterogeneous catalysts.

A

Haber process: Solid iron catalyst used

Contact process, SO2 + O2: Solid V2O2 used

Hydrogenation: solid Nickel catalyst used.

Decomposition of hydrogen peroxide: Manganese (IV) oxide solid is used (MnO2)

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12
Q

Give an example of how a transition metal acts as a homogeneous catalyst.

A

Reaction between iodide ions and peroxodisulfate ions:

Fe3+ (aq) catalyst used.

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13
Q

What is a monodentate ligand?

A

A ligand that donates ONE pair of electrons to a central metal ion.

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14
Q

What is the shape of a complex ion with a co-ordinate number of six?

A

Octahedral: 90 degree bond angle.

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15
Q

Shape of a complex ion with co-ordinate number:
2
4
5

A

2: linear- 180 degrees
4: tetrahedral (109.5 degree)/ square-planar- 90 degrees
5: trigonal bipyramidal- 90 and 120 degrees

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16
Q

What type of isomerism can occur in complex ions?

A

Stereoisomerism:

Optical
Cis-Trans

17
Q

Cis-Trans isomerism in complex ions.

A

Can occur in complex ions with:

4/6 co-ordinate bonds that are monodentate, with 2 different monodentate

6 co-ordinate bonds with monodentate and/or bidentate ligands

Cis- Same ligands are adjacent (90 degrees)
Trans- Same ligands are opposite (180 degree)

18
Q

Optical isomerism in complex ions.

A

Occurs in complex ions with:

6 co-ordinate bonds that contains two or more bidentate ligands.

Trans isomers are not optical isomers as they form symmetrical molecules.

19
Q

How can you differentiate between two complex ion, optical isomers?

A

Pass the molecules through plane polarised light.

Each isomer will rotate the light in a different direction.

20
Q

Describe Platin and how it is used in medicine.

A

Platin: Pt(NH3)Cl2

Cis-Platin is used in chemotherapy to shrink and stop cancerous growth.

Cis-Platin attaches to DNA and prevents DNA replication which prevents cell division.
This leads to cell mechanism uniting apoptosis.

However: negative side effects include kidney damage

21
Q

Describe how haemoglobin uses a complex ion?

A

Contains haem group:
Fe2+ and porphyrin ring with 4 nitrogens

This forms an octahedral structure with two bonds free.

One bond can attach to a polypeptide in a protein.

Another bond can attach to a molecule of oxygen.

Carbon monoxide can displace oxygen as it form a strong bond with Fe2+

22
Q

Describe the reaction between Copper (II) and OH-

A

Precipitation reaction:

Copper solution is original light blue

A light blue Copper Hydroxide precipitate forms. This is not soluble in excess OH-

This ppt is soluble in excess ammonia to form a deep blue solution: Cu(NH3)4 (H2O)2

23
Q

Colour of Cu2+ solution

A

Light blue

24
Q

Colour of Cu(OH)2 precipitate

A

Light blue

25
Q

Colour of Cu(NH3)4(H2O)2

A

Deep blue

26
Q

Describe the reaction of Mn2+ with hydroxide ions

A

Mn2+ is originally a pale pink solution

It forms a light brown precipitate: Mn(OH)2

Pale pink—> light brown

Precipitate is not soluble in excess OH-

27
Q

Describe the reaction between Fe2+ and hydroxide ions

A

Fe2+ is originally a green solution

It forms a green precipitate: Fe(OH)2

Green —-> green ppt

Precipitate is not soluble in excess OH-

Precipitate can be oxidised to an orange brown ppt—> Fe(OH)3

28
Q

Reaction between Fe3+ and hydroxide ions

A

Fe3+ is originally a yellow solution

An orange/ brown precipitate forms

Yellow —> orange/brown

The precipitate is not soluble in excess OH-

29
Q

Reaction between Cr3+ and hydroxide ions

A

Cr3+ is originally a violet solution

It forms a grey-green ppt: Cr(OH)3

It is soluble in excess NH3: forms purple solution

Also soluble in excess OH-: forms dark green solution

30
Q

Describe the qualitative analysis when oxidising Fe2+

A

Fe2+ is reacted with MnO4-, an oxidising agent.

MnO4- is added in a burette and is initially purple.
A colour change from colourless to light pink the the conical flask confirms the end point.

31
Q

Describe the qualitative analysis when reducing Fe3+

A

Iodide ions are used as a reducing agent.

Fe3+ is originally orange/brown.

The solution turns brown as Iodide ions are oxidised to Iodine.

Fe3+ is reduced to Fe2+ (which is pale green).

32
Q

Describe the qualitative analysis when reducing Cr2O7 2-

A

Zinc is used as a reducing agent, with HCl or H2SO4.

Dichromate is originally orange but then is reduced to a green colour- Cr3+

This is further reduced to Cr2+ which forms a pale blue solution. This only occurs when there is an excess of zinc.

33
Q

Describe the qualitative analysis when oxidising Cr3+

A

Cr3+ is reacted with hot, alkaline Hydrogen peroxide.

Cr3+ is oxidised with hydroxide ions and H2O2.

This shows a colour change from green to orange (CrO4 2-).

34
Q

Describe the qualitative analysis when reducing Cu2+.

A

Cu2+ reacts with excess iodide ions.

Iodide ions are oxidised to iodine, which forms a brown solution.

Cu2+ is originally pale blue but a white precipitate forms when CuI(s) is formed.

Chemistry, Module 5 OCR (6 decks)

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