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Chemistry > Transition Metals > Flashcards

Transition Metals Flashcards

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1
Q

Define transition metal

A

d-block elements that have an ion with a incomplete d-sub-shell

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2
Q

Give two examples of transition metals with more than one oxidation state

A

Fe2+ Fe3+

Cr2+ Cr3+ Cr6+

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3
Q

Name the two elements that one would think to be transition metals but technically aren’t

A

Scandium and Zinc, because their ions have full and empty d-sub-shells

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4
Q

State three main physical properties of transition metals compared to other metals

A

They have higher melting points, boiling points, and densities.

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5
Q

Why do transition metals have variable oxidation states

A

Because the electrons in 3d and 4s subshells are of similar energy, so transition metal can lose different numbers of electrons to form ions with similar stability

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6
Q

Why can transition metals form complex ions

A

Many transition metals have empty spaces in their 3d-orbitals, so they can receive lone pairs from other species, forming dative covalent bonds.

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7
Q

Why are transition metal compounds coloured

A

When electrons move from a d-orbital with lower energy to a d-orbital with higher energy, energy is taken in. This energy is in the form of visible light, which is absorbed. Only certain frequencies are absorbed, so all the other frequencies are reflected, producing colour.

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8
Q

What is a complex ion

A

An ion in which a central positive ion is surrounded by ligands, which are coordinately bonded (datively) to it.

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9
Q

What are the four main ligands

A

Water molecules, OH-, NH3 and CN-

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10
Q

What is a ligand

A

A molecule or negative ion which has a lone pair of electrons which can be used to form a coordinate bond with a metal ion

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11
Q

Why are transition metals more susceptible to forming complexes

A

They are small and polarising, since their nuclei are poorly shielded, so they attract ligands strongly.

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12
Q

How do you name a complex ion

A

No. ligand, name of ligand, name of transition metal (ending in -ate if negative), charge

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13
Q

Give an example of a complex ion with each shape

A

Linear - [CuCl2]-
Tetrahedral - [CrCl4]-
Planar - [Pt(NH3)2Cl2]
Octahedral - [Cu(H2O)6]2+

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14
Q

Give two examples of a polydentate ligand

A

1,2-diaminoethane

EDTA

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15
Q

What are the complex ions involved in adding concentrated HCl to aqueous CuSO4 solution, then adding NH3 and what is the colour change

A

[Cu(H2O)6]2+ Blue
[CuCl4)2- Green
[Cu(NH3)4(H2O)2]2+ Deep blue

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16
Q

What is the colour change that accompanies the formation of [Cr(NH3)6]3+ from [Cr(H2O)6]3+

A

Hexaaquachromium(III)3+ is green, and it turns to purple

17
Q

What are the colours of Fe2+ with Water, Ammonia, Hydroxide, also in excess

A 
Water - green
NH3 - Dark green ppt
E NH3 - Insoluble
OH - Dark green ppt
E OH - Insoluble

NB all of OH and NH3 are the same because NH3 (not in excess) uses OH- ions

18
Q

Colours of Cu2+

A 
Water - Blue
NH3 - Pale blue ppt
E NH3 - Deep blue solution
OH - Pale blue ppt
E OH - Insoluble
19
Q

Colours of Mn2+

A 
Water - Pink
NH3 - Buff ppt
E NH3 - Insoluble
OH - Buff ppt
E OH - insoluble
20
Q

Colours of Fe3+

A 
Water - Yellow
NH3 - Orange/brown ppt
E NH3 - Insoluble
OH - Orange/brown ppt
E OH - Insoluble
21
Q

Colours of Cr3+

A 
Water - Violet
NH3 - Green -grey ppt
E NH3 - Purple blue solution
OH - Green -grey ppt
E OH - Dark Green solution
22
Q

The disproportionation of Cu+

A

When dissolved in water disproportionates to Cu(s) and Cu2+(aq). Colour change is from white solids to a red-brown solid and a blue solution.

23
Q

The reduction of Cu2+

A

Cu2+ ions will react with iodide ions forming white CuI(s) and I2

24
Q

What are the colours of the oxidation states of Cr

A

Cr2+ is blue
Cr3+ is Green
CrO4 2- is Yellow
Cr2O7 2- is Orange

25
Q

What are the conversions between the oxidation states of Cr

A

Cr(OH)6 3+ is combined with H2O2 and boiled to make CrO4 2-, hydroxide and water

Cr2O7 is favoured in acidic conditions, CrO4 is favoured in alkaline conditions, so add H+ to make dichromate and add water to make chromate

Cr3+ is reduced by adding solid zinc, 2Cr3+ + Zn–>2Cr2+ + Zn2+

Cr2O7 2- + 14H+ + 6Fe2+ —> 2Cr3+ + 7H2O + 6Fe3+

26
Q

Uses of chromium

A

Used in stainless steel which resists corrosion. It is also added to iron in smaller amounts to make hard alloy steels

27
Q

Give examples of transition metals being used as catalysts

A

Iron is used in the Haber process

Nickel is used in margarine production to hydrogenate unsaturated hydrocarbons

28
Q

The reduction of MnO4-

A

MnO4- + 5e- + 8H+ –>Mn2+ 4H2O

Chemistry (17 decks)

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