Transition Metals Flashcards by Daniel Deane

What is a transition metal

Element in the ‘d block’ with a partially filled d-orbital

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Special properties of transition metals

Form complexes
Form coloured ions
Variable oxidation states
Good catalysts

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What is a complex

Central metal ipn surrounded by ligands

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Common ligands are…

Cl-
H²O
NH³

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What is a ligand

Molecules or ions with a lone pair of electrons that is able to form a co-ordinate bond with the central metal ion.

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What is a co-ordination number

The number of co-ordinate bonds formed around the central metal ion.

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Why do NH³ and H²O not change the co-ordination number when exchanged in ligand substitution reactions

Are both uncharged and similar in size

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Colour of [Cu(H²O)²(NH³)⁴]²+ solution

Deep blue

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Why does Cl- affect the co-ordination number

Cl- ligand is larger than NH³ and H²O

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How many Cl- ligands can attach to a metal ion.

And shape of complex

Tetrahedral

Bond angle 109.5

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What is a Bidentate Ligand

Ligands that form 2 co-ordinate bonds to the central ion and have 2 lone pairs of electrons

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2 examples of Bidentate ligands

C²O⁴ (OOCCOO)
Lone pairs on single bond O’s

NH²CH²CH²NH²
Lone pairs on N’s

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How many ligands does a Bidentate ligand replace
Does co-ordination number change

2
No change, still has 6 co-ordinate bonds

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What is a Multidentate ligand

Ligand that can form up to 6 co-ordinate bonds to central metal ion.

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Most common multidentste ligand

EDTA⁴-

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What is the Chelate effect

Substituting unidentate ligands with bidentate or multidentare ligands to form more stable complexes.

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What type of entropy is favourable in a ligand substitution reaction and why

Positive, more stable complex is being formed.
More favourable to have more moles on right than left

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When will /\G be more favourable

The more negative /\G is the more favourable the reaction

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What is the size of the enthalpy change (/\H) of ligand substitution reactions and why

/\H is very small
The bonds being formed are similar to the bonds broken
So overall enthalpy change is close to 0

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What ligands commonly fork octahedral complexes

Bond angle of complex

NH³
H²O

90°

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How is cis and trans isomers present in octahedral complexes

Cis - same unidentste ligands next to each other.
In planar positions

Trans - same unidentate ligands opposite each other.
E.g top and bottom

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What complexes have optical isomerism

Octahedral complexes with bidentate ligands

Mirror images of each other

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How is a tetrahedral complex formed

Bond angle

When complexes form with large ligands such as Cl-

Bond angle 109.5°

Do tetrahedral complexes have optical isomerism

Yes

What metals form square planar complexes Bond angle

Platinum (Pt) Nickel (Ni) 90°

What metal(s) form linear complexes Bond angle

Silver (Ag) 180°

What is Cisplatin

Cis isomer of square planar complexes of Platinum (Pt)

Common use of Cisplatin

Cancer therapy drug

Why does only the cis isomer of the square planar platinum (Pt) work as a drug fir cancer therapy

Cells are chiral so only cis isomers are the correct orientation to 'fit' the cells.

A Side effect of Cisplatin And measure to reduce effect

Hair loss Administered in small amounts to reduce effects

What affects the colour of a transition metal ion (3)

Co-ordination number Type of ligands bonded to the ion Oxidation state

How is colour of the ions observed

White light shined on metal ion Some wavelengths are absorbed Remaining wavelengths are reflected back to the human eye The reflected wavelengths forrespond to specific colours

What happens to electrons in the d-orbital when they absorb energy from light

Move from ground state and are promoted to a higher state

How to calculate /\E between two energy states of electrons

/\E = (h x speed of light)/wavelength = h x frequency h=planks constant 6.63x10^-34

What is colorimetry

Analytical technique that uses absorption of light to determine the concentration of coloured ions

How is a calibration graph for colorimetry produced

Measuring solutions of known concentrations against absorbance Relative abundance y axis Concentration x axis

How is a calibration graph for colorimetry used

To determine the concentration of an unknown substance

Vanadium 4 possible colours with oxidation states and ions

5+ VO2+ yellow 4+ VO²+ blue 3+ V³+ green 2+ V²+ violet You Better Get Vandadium

What determines if a transition metal is reduced or oxidised

The pH of the reaction conditions

What conditions are required to reduce a transition metal

Acidic conditions H+ ions in excess

What conditions are required to oxidise transition metals

Alkaline OH- in excess

3 reactions used in redox titrations

MnO4- + 8H+ + 5e- —> Mn²+ + 4H2O Fe2+ —> fe³+ + e- C2O4²- —> 2CO2 + 2e-

In a redox titration what is the ratio between MnO4- ions to C2O4²- ions

2 : 5

In a redox titration what is the ratio between Mno4- ions to Fe²+ ions

1 : 5

In a redox titration what is the ratio between C2O4²- ions to Fe²+ ions

1 : 2

What is catalyst

A substance that speeds up the rate of reaction without being used up

Do catalysts affect equilibirum

No But allow it to be reached faster

2 types of catalysts

Homogenous Heterogenous

What is a heterogenous catalyst

A catalyst that is in phase or state to the species in the reaction

Why are transition metals good catalysts

Variable oxidation states Electrons are transfered to produce a reactive intermediate

What transition metal is used in the haber process

Solid iron catalyst

What transition metal is in the contact process

Vanadium oxide

What is the contact process

Conversion of SO2 to SO3

How does a catalyst work

Absorbs molecules onto active site Active site increases proximity of molecules and weakens covalent bonds Increases rate Molecules are resorbed after they react

How are catalysts poisoned

When impurities bpock active sites and prevent adsorption

What is a homogenous catalyst

Catalysts that are in the same phase to the species of the reaction

What is autocatalysis

Where a product in a reaction acts as a catalyst for the reaction