Transition Metals Flashcards
what is a transition metal?
metals that can form one or more stable ions w a partially filled d sub-shell
where are transition metals found in periodic table?
d-block
which orbital fills first 3d or 4s? And what is the exception in two transition metals?
4s fills first
Cr and Cu are exceptions
- Cr prefers to have 1 electron in each orbital of 3d sub-shell & just 1 in 4s sub-level, gives it more stability
- Cu prefers to have full 3d sub-level and just 1 electron in 4s sub-level, more stable
which orbital are electrons lost first from, 3d or 4s?
4s
why aren’t Sc and Zn transition elements?
Sc forms one ion Sc^3+ which has an empty 3d sub-level
Zn forms one ion Zn^2+ which has a full 3d sub-level
(transition metals form stable ions with PARTIALLY filled d sub-levels)
physical properties of transition metals
high density
high MP and BP
‘same’ ionic radii (more or less)
chemical properties of transition metals
they act as good catalysts
they exist in variable oxidation states
they can form complex ions
they can form coloured ions in solution
why do transition metals have variable oxidation states?
- the electrons sit in 4s and 3d energy levels which are very close
- so electrons are gained and lost using similar amount of energy when they form their ions
what ions do Scandium form and state oxidation states?
Sc^3+ (Oxidation state: +3)
what ions do Vanadium form and state oxidation states?
V2+ (+2), V^3+ (+3), VO^2+ (+4), VO2+ (+5)
what ions do Chromium form and state oxidation states?
Cr^3+ (+3) and Cr2O7^2- (+6)
what ions do Manganese form and state oxidation states?
Mn^2+ (+2) and MnO4- (+7)
what ions do Iron form and state oxidation states?
Fe^2+ (+2) and Fe^3+ (+3)
what ions do Cobalt form and state oxidation states?
Co^2+ (+2)
what ions do Nickel form and state oxidation states?
Ni^2+ (+2)
what ions doCopper form and state oxidation states?
Cu^2+ (+2)
what ions do Zinc form and state oxidation states?
Zn^2+ (+2)
state colours of vanadium ions formed
V2+ violet when surrounded by 6H2O, they’re normally substituted so usually look green
V^3+ green
VO^2+ blue
VO2+ yellow
state colours of chromate and dichromate ions formed
Cr2O7^2- orange
Cr^3+ violet, 6H20 usually substituted so appears green sometimes
state colours of Manganate ions formed
MnO4^- purple
Mn^2+ pale pink
state colours of Iron ions formed
Fe^2+ pale green
Fe^3+ orange/yellow
state colours of Cobalt ion formed
Co^2+ pink
state colours of Nickel ion formed
Ni^2+ green
state colours of Copper ion formed
Cu^2+ blue
what is a complex?
central atom or ion surrounded by co-ordinatedly bonded ligands
what is a co-ordinate bond?
(or dative covalent bond)
covalent bond where both electrons are in shared pair come from SAME atom
- in a complex they come from the ligands
what is a ligand?
- atom/ion/molecule that donates a pair of electrons to central transition metal ion to form a co-ordinate bond
(they must have at least 1 pair of lone electrons) - can be monodentate, bidentate or polydentate
what is the co-ordinate number?
the number of co-ordinate bonds that are formed with the central metal ion
(not the number of ligands)
monodentate ligands
ligands which have one lone pair of electrons examples: H2O: \:NH3 \:Cl-
bidentate ligands
ligands which have two lone pairs of electrons
examples:
ethanedioate C ₂O²⁻ ₄
ethane-1,2-diamine C₂H₄(NH₂)
multidentate ligands
ligand capable of donating two or more pairs of electrons (to from co-ordinate bonds)
examples:
Haem
EDTA^4- (forms 6 co-ordinate bonds w central metal ion)
which are small ligands and what does this mean for complex shapes?
H2O:
:NH3
- means 6 can fit around central metal ion forming octahedral shape (bond angles 90 degrees)
which are bigger ligands and what does this mean for complex shapes?
:Cl-
- can only fit 4 ligands around central metal ion (usually forming tetrahedral shape, bond angle is 109.5 degrees, BUT can also form square planar e.g. cisplatin bond angles 90 degrees)
what kind of size are these ligands: ethanedioate and ethane-1,2-diamine? and how many can fit around a central ion?
- they are ‘larger’ (than the other ones e.g. :Cl-)
- three
complexes with co-ordinate number two form what coplex shapes? Give an example
- form linear shapes (bond angle is 180 degrees)
- some silver complexes e.g. [Ag(NH3)2}+ (this is tollens reagent/silver mirror)
How do you work out oxidation state of metal ion?
total oxidation state - total oxidation state of ligands
a complex’s overall charge is the same as its what?
its total oxidation state (number and charge outside square bracket)
what is haem?
a multidentate ligand that is found in molecule haemoglobin
what is haemoglobin?
quarternary protein used to transport oxygen around body in blood
what do the ligands NH3 and H2O have in common?
similar in size and are uncharged
exchnage of ligands NH3 and H2O occurs without what?
without change of co-ordination number (eg Co2+ and Cu2+)
what occurs when you dissolve the salt of a transition metal in water?
- becomes surrounded by water molceules acting as ligands
called aqua ions
what kind of isomers can transition metals form?
optical isomers and geometric (E-Z) isomers
what kind of complexes does geometric isomerism occur in?
octahedral and square planar
in what complexes does optical isomerism occur?
- this occurs when there are two or more bidentate ligands in a complex
