Transition Metals

what factors affect the relative stabilities of different oxidation states

the electronic structure

the type of bonding involved

the stereochemistry

what are monodendate ligands

ligands which form a dative bond/ donate one pair of electrons to the central transition metal ion

when does a complex appear colourless

none of the EM spectrum is absrobed

what is the crystal field strength

energy difference between 2 subsets of d orbitals

the greater the crystal field strength, the more energy required to promote an electron from the lower group of d orbitals to the higher ones

the greater the energy absorbed, the higher the frequency of emitted light

why do complexes of the same metal ion with different ligands have different colours

different ligands produce difference crystal field splittings

these depend on the position of the ligand in the SPECTROCHEMICAL SERIES

what is the catalyst for the Ostwald process

platinum

which two transition metals do NOT follow the aufbau principle

copper

chromium

what is formed when ligands surround a central transition metal ion

a transition metal complex called a coordination compound is formed

give some examples of monodendate ligands

chloride ion

cyanide ion

ammonia molecule

water molecule

why is EDTA described as a hexadendate ligand

Has 6 non-bonding pairs of electrons which bond to the transition metal ion

what is the shape of a complex ion with coordination number 4

square planar OR tetrahedral

when is UV spectroscopy used

when the absorbed energy is in the UV part of the EM spectrum (and hence the compound is colourless)

what is the catalyst for the haber process

iron

what are the catalysts used in catalytic converters

platinum

palladium

rhodium

what catalyst is used in the hardening of oil to make margarine

nickel

what is the oxidation state of fluorine in compounds

-1

what is an example of a quadridentate ligand

haemoglobin

what is the latin name for copper

cuprate

what are the two subsets of d-orbitals formed upon splitting of the d sub shell

the ground state (lower energy)

the excited state (higher energy)

which ion do not obey the theory behind the spectrochemical series

ions which don't have 1-9 d electrons (as they can't have d-d transitions)

what makes up the d block elements

the transition metals

what are some uses of transition metals

piping

electrical wiring

coinage

construction

jewellery

industrial catalysts

what gives transition metals their distinctive properties

at least one of their ions has a partially filled d sub shell

why do copper and chromium not follow the aufbau principle

their half-filled d orbitals have a special stability so each 4s sub shell is half filled (and in Chromium all of the d orbitals are also half filled)

where are electrons first lost from when transition metals form ions

the outermost shell (e.g. the 4s in copper and chromium)

Why are scandium and zinc not considered transition metals?

their stable ions do not have partially filled d-orbitals (Zn2+ has a fully filled d sub-shell, Sc3+ has an empty d sub-shell)

what elements have similar chemical properties to Zn

the group 2 metals (Mg and Ca)

what are the rules when assigning an oxidation number to an element

uncombined elements have oxidation numbers of 0

for monatomic atoms, the oxidation number is the same as the charge on the ion

oxygen has oxidation -2 for most compounds

hydrogen has oxidation number +1 in most compounds but -1 in metallic hydrides

the sum of all oxidation numbers in a molecule/ neutral compound must add up to 0

the sum of all oxidation numbers in a polyatomic ion must add up to the charge of the ion

what factor can affect the colour of a transition metal

its oxidation state

which metal compounds are typically oxidising agents

metal compounds in high oxidation states

which metal compounds are typically reducing agents

metal compounds in low oxidation states

what are ligands

molecules which can donate at least one lone pair of electrons and form a co-ordinate/ dative covalent bond with a metal

what are bidendate ligands

donate 2 pairs of electrons to the central transition metal ion

what are some examples of bidendate ligands

oxalate

ethylenediamine

what is the coordination number of the central transition metal ion

the number of dative covalent bonds to the metal atom/ ion from the ligand

what is the shape of a complex ion with coordination number 2

linear

what is the shape of a complex ion with coordination number 6

octahedral

how do you name transition metal complexes

symbol of metal written followed by symbols of ligands in alphabetical order according to which atom of the ligand binds (e.g. OH2 instead of H2O is the O binds to the metal)

Formula is enclosed within square brackets with charge on the outside

Ligands named in alphabetical order followed by metal name and oxidation state (prefixes added on)

Oxidation state of central metal atom is written in Roman numerals

when naming transition metal complexes, what happens to the name of ligands which are negative ions ending in ide

ending changes to 'o' e.g. chlorido

what are the names for ammonia and water in transition metal complexes

ammine and aqua

how do you name transition metal complexes that are negative ions overall

complex ends in -ate

Latin name is used except for with mercury

how do you name transition metal complexes which are salts

name of the positive ion precedes the name of the negative ion

when does a complex appear coloured

some of the EM spectrum is absorbed

when does a complex appear black

all of the EM spectrum is absorbed

why are transition metal complexes able to absorb light?

splitting of the 5 degenerate d orbitals

explain the splitting of the 5 degenerate d orbitals in transition metal complexes

when the metal is unbounded, there are 5 degenerate d orbitals

ligands surround the central ion along the x,y and z axes

electrons in d orbitals along these axes are repelled by electrons in the ligands

d subshell is split into two distinct sets of orbitals with an energy difference between them

axis orbitals have higher energy than those between the axes so the d orbitals are no longer degenerate

what determines the energy difference between the subsets of d orbitals

the position of the ligand in the spectrochemical series

the transition metal ion

the oxidation state of the transition metal

the type of ligand

the coordination number of the metal

what is the spectrochemical series

the series of order of a ligand's ability to split d orbitals

what light is emitted when a certain wavelength of light is absorbed by a compound

the complementary colour to that which was absorbed

what happens when transition metal complexes absorb light

electrons in lower d orbitals absorb energy and move up to higher d orbitals

if energy absorbed in the d-d transition is in the visible light region of the EM spectrum the colour of the transition metal will be COMPLEMENTARY to that of the colour absorbed

what is the wavelength range of the visible spectrum

400-700nm

when can visible spectroscopy be used

if the absorbed energy is in the visible part of the EM spectrum

what is the wavelength range for UV light

200-400nm

what are strong field ligands

those that cause the greatest splitting of d orbitals

what are weak field ligands

those that split d orbitals the least

how does the strength of ligands affect which region of the EM spectrum is likely to be absorbed by the complex?

strong field ligands are more likely to absorb energy in the UV section

Weak field ligands are more likely to absorb energy in the visible spectrum

what coloured filter should be used when measuring the absorbance of coloured solutions using colorimetry

the complementary colour to the sample

what catalyst is used in the contact process

Vanadium(V) oxide

name some transition metals used for effective catalytic activity of enzymes

iron

copper

manganese

cobalt

nickel

chromium

give an account of chemisorption

atoms on the surface of the active sites form weak bonds with reactant molecules using PARTIALLY FILLED/ EMPTY D ORBITALS

These form intermediate complexes with weakened covalent bonds (i.e. the reactants are ADSORBED onto the active sites) AND in favourable orientation to collide with other reactant molecules

Hence reducing the activation energy

what is the difference between oxidation state and oxidation number

nothing; they are both interchangeable

what is the oxidation state of oxygen in peroxides

-1

what happens to oxidation number during oxidation

increases

what happens to oxidation number during reduction

decreases

what are the colour changes for the vanadium ion

+5 = yellow

+4 = blue

+3 = green

+2 = violet

You Better Get Vanadium

what is the colour change for dichromate

orange to green upon reduction

+6 to +3

what is the colour change for acidified permanganate

purple to colourless

+7 to +2

what is a co-ordinate bond

dative covalent bond

both electrons in the bond are donated from the same species

in complexes, the lone pair is donated into an empty orbital in the transition metal atom/ ion

what are quadridentate ligands

molecules which donate 4 lone pairs of electrons/ form 4 co-ordinate bonds with the central metal atom/ ion

what are lewis acids

the metals that accept electrons in co-ordination compounds

what are lewis bases

the ligands that donate electrons in co-ordination compounds

what are the names for sulfate and nitrite when they are part of a co-ordination complex

sulfato

nitrito

what prefixes are used for polydendate ligands when they occur more than once?

bis-, tris-, -tetrakis, etc.

what is the order in which the names of the ligands are written?

neutral, negative, positive

when the same charge is present, they are named alphabetically

what is the latin name for iron

ferrate

what is the latin name for tin?

stannate

what its the latin name for silver

argentate

what is the latin name for lead

plumbate

what is the colour observed when a metal absorbs red light

cyan (mix of blue and green)

what is the colour absorbed when a metal absorbs green light

magenta (mix of red and blue)

what is the colour absorbed when a metal absorbs blue light

yellow (mix of red and green)

How do heterogeneous catalysts work?

through chemisorption

why are transition metals able to act as homogeneous catalysts

they have a variety of oxidation states so they can provide alternative reaction pathways

what is the colour change observed when cobalt is used to catalyse the oxidation of Rochelle salt

pink (2+)

green (3+)

pink (2+)

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