5.3 Transition metals Flashcards by Raphaella Ridley

What is a transition element (metal)?

a d-block element that has an incomplete d-sub-shell as a stable ion

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Which d-block elements are not transition metals and why?

scandium and zinc

- they do no have ions with partially filled d-orbitals

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Which elements have irregular orbital filling patterns?

CHROMIUM - the five 3d-orbitals and the 4s orbital all contain one electron
COPPER - the five 3d orbitals are full, there is only one electron in the 4s orbital

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Which electrons do transition element ions lose first?

4s before 3d because, once electrons occupy the orbitals, the 4s electrons have a higher energy and are lost first

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Physical properties of transition metals

lustrous in appearance
high densities
high melting and boiling points
can conduct electricity

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Chemical properties of transition metals

different oxidation states
form coloured solutions when dissolved in water
often used as catalysts

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Are transition metals powerful reducing or oxidising agents?

oxidising

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Example of disproportiation reaction of transition metal

adding hot dilute sulphuric acid to copper (I) oxide we form blue solution of Cu (II) sulphate and brown precipitate of copper solid
Cu2O + H2SO4 = Cu + CuSO4 + H2O

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Why are different colours associated with transition metals?

movement of electrons in partially filled d-orbitals

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Two ways transition metals act as catalysts

provide a surface for reaction to take place (atoms absorb onto surface and held in place)
can change their oxidation states (bind to reactants and form intermediates)

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Disadvantages of using transition metals as catalysts in industry

can be toxic or damaging to environment

- must be disposed of carefully

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Describe Haber process reaction and catalyst

N2 + 3H2 = 2NH3
iron metal (increases rate and lower temp)
ammonia used for agricultural fetilisers

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Describe contact process reaction and catalyst

2SO2(g) + O2(g) = 2SO3 (g)

vanadium (V) oxide, V2O5

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What is SO3 from the contact process used for?

To manufacture sulfuric acid which is use for:

fertilisers
detergents
adhesives
explosives
electrolyte in car batteries

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Describe decomposition of hydrogen peroxide and catalyst

2H2O2 = 2H2O +O2

manganese (IV) oxide, MnO2

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What is decomposition of hydrogen peroxide used for?

preparation of oxygen gas

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Describe hydrogen production and catalyst

Zn(s) + H2SO4(aq) = ZnSO4(aq) + H2 (g)

CuSO4 catalyst`

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What is a complex ion?

a transition metal ion bonded to one or more ligands by coordinate (dative covalent bonds)

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What is a ligand?

a molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond

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What is the coordination number?

the total number of coordinate bonds formed between a central metal ion and its ligands

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When are complex ions formed?

When transition metal compounds are present in a solution

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What is a monodentate ligand?

the ligand donates just one pair of electrons to the central metal ion to form one coordinate bond

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What monodentate Ligands do we need to know?

OH2 (water)
NH3 (ammonia)
Chloride Cl-

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What are bidentate ligands?

have two pairs of electrons from different atoms to donate to the central metal so two coordinate bonds can form

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What is the most common bidentate ligand and what is it shortened to?

ethane-1,2-diamine, NH2CH2CH2NH2 shortened to 'en' each nitrogen donates a lone pair

How many coordinate bonds does a octahedral complex have and what are the bond angles?

6 | 90 or 180

Why can only four chloride ligands fit around the metal ion?

they are big

What complexes do chloride ions form?

tetrahedral

What is a square planar complex?

Where four monodentate ligands arrange themselves in the same plane at the metal atom

Define stereoisomerism

species with them same structural formula but with a different arrangement of atoms in space

What are the two types of stereoisomerism in transitional element chemistry?

cis-trans isomerism | optical isomerism

Colour of Cu2+ in solution

Blue

Colour of Fe2+ in solution

Green

Colour of Fe3+ in solution

Yellow

Colour of Mn2+ in solution

Pink

Colour of Cr3+ in solution

Violet (often green)

Colour of Cu2+ after addition of NaOH/NH3

Blue ppt (Cu(OH)2)

Colour of Fe2+ after addition of NaOH/NH3

Green ppt. Fe(OH)2

Colour of Fe3+ after addition of NaOH/NH3

Brown ppt. Fe(OH)3

Colour of Mn2+ after addition of NaOH/NH3

Brown ppt. Mn(OH)2

Colour of Cr3+ after addition of NaOH/NH3

Green grey ppt. Cr(OH)3

`Colour of Cr3+ after addition of excess NaOH

Green sol. [Cr(OH6)]3-

Colour of Cu2+ after addition of excess NH3

Dark blue sol. [Cu(H2O)2(NH3)4]2+

Colour of Cr3+ after adding excess NH3

Purple sol. [Cr(NH3)6]3+

What is ligand substitution?

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

`What does an aqueous solution of Cu2+ ions form?

[Cu(H2O)6]2+ complex ions

What colour are [Cu(H2O)6]2+ ions?

blue

What is the colour change when [Cu(H2O)6]2+ is added to NH3?

blue to deep blue

Equation for the reaction between aqueous Cu2+ ions and NH3

[Cu(H2O)6]2+ (aq) + 4NH3 = [Cu(NH3)4(H2O)2]2+ (aq) + 4H2O (l)

Two observations shown when carrying out the reaction between Cu2+ and ammonia experimentally

1) blue ppt of Cu(OH)2 forms (small amount of ammonia) | 2) deep blue solution formed with excess ammonia

Colour change when HCl is added to Cu2+?

pale blue to green to yellow

How do you reverse the reaction between HCl and Cu2+?

By adding water

Equilibrium between Cu2+ and HCl reaction

[Cu(H2O)6]2+(aq) + 4Cl-(aq) = [CuCl4]2-(aq) +6H2O(l)

Why does [Cu(H2O)6]2+(aq) have 6 ligands but [CuCl4]2-(aq) only has four?

Chloride ligands are larger than water ligands and have stronger repulsion

Equation for the reaction between chromium (III) and excess ammonia

[Cr(H2O)6]3+ +6NH3 = [Cr(NH3)6]3+ +6H2O

What ions does aqueous solution of chromium (III) contain?

[Cr(H2O)6]3+

[Cr(H2O)6]3+ colour

violet

Colour change of reaction between chromium (III) and excess ammonia

violet to purple

Describe the coordinate bonds on Fe2+ in haem

- four coordinate bonds between Fe2+ and nitrogen - one coordinate to globin protein - final coordinate bonds to O2

Why is CO dangerous?

It binds more strongly to haem the O2 | Not reversible

What are the three typical reactions of transition metals?

Precipitation Ligand substitution Redox

What two species do we need to know the ligand substitution reactions of?

[Cr(H2O)6]3+ | [Cu(H2O)6]2+

Example of a precipitation reaction

Cu2+ + 2OH- = Cu(OH)2

Four redox reactions that we need to know

Fe2+ = Fe3+ + e- 2Cr3+ +7H2O = Cr2O72- + 14H+ +6e- Cu2+ + e- = CuI + I2 Cu+ = Cu + Cu2+

What is needed for Fe2+ = Fe3+ + e-?

H+/MnO4-

What is needed for Fe3+ + e- = Fe2+ ?

I-

What is needed for 2Cr3+ +7H2O = Cr2O72- + 14H+ +6e-?

H2O2/OH-

What is needed for Cr2O72- + 14H+ +6e- = 2Cr3+ +7H2O?

Zn/H+

What is needed for Cu2+ + e- = CuI + I2

I-

What colour is CuI?

White precipitate

What colour is I2 and state?

brown/yellow solid

What colour is Cu+?

light brown/ yellow solid

What colour is Cu metal?

red/orange

Example of octahedral complex ion?

[Cu(H2O)6]2+ | [Fe(H2O)6]3+

Example of tetrahedral complex ion?

[CuCl4]2– | [CoCl4]2–

Example of square planar complex ion?

Pt(NH3)2Cl2

Requirements for optical isomerism of transition elements

- three bidentates - two bidentates and two monodentates - one hexadentate ligand

What is cis-platin?

Anti-cancer drug PtCl2(NH3)2 Binds to DNA of cancer cells to prevent cell division

Benefits and risks of cis-platin

Benefits of chemotherapy | Unpleasant side effects

5.3 Transition metals Flashcards

(79 cards)