24 - transition elements Flashcards
what is a d block element
element where highest energy electron is in the d subshell
what are some general properties of metals
metallic
high m.p / b.p
shiny
conduct electricity + heat
what are the exceptions to the redox rules
Cr
Cu
what is a transition metal
d block elements that form at least 1 ion with a partially filled d-orbital
which d block elements are not transition metals
scandium + zinc
why is scandium not a transition metal
atomic number - 21
does not form an ion with a partially filled d orbital - has an empty d orbital
why is zinc not a transition metal
atomic number - 30
does not form an ion with a partially filled d orbital - has a full d orbital
what are the properties specific to transition metals
form ions with variable oxidation states
forms coloured compounds
act as catalysts
what is the oxidation state that all transition metals have
+2
colour of potassium dichromate
bright orange
colour of Cobalt (II) chloride
pink purple
colour of Cr04
yellow
how do transition elements form coloured compounds
linked to partially filled d orbitals
what happens if you dissolve a coloured compound
make coloured solutions
benefits + risks of using transition metals as catalysts
Benefits – reduces energy usage / lower costs
Risks – toxicity of many transition metals
examples of reactions where the transition metal is a heterogenous catalyst
examples of reactions where the transition metal is a heterogenous catalyst
what is a complex ion
Consists of a central metal ion with one or more molecules / charged ions (ligands) bound to it by dative covalent bonds
what are complex ions formed from
Formed by d-block elements
+ other elements – Aluminium
what is a ligand
Molecule / ion that donates a pair of electrons to a central metal atom by coordinate / dative covalent bonding
what is needed for something to be a ligand
Lone pairs needed
what are some neutral ligands
water / ammonia
what are some charged ligands
halide ions / CN- / hydroxide
how is a complex ion written out
what is the coordination number
Number of coordinate bonds made to the central metal atom
shape / bond angle / examples of coordination number 6
Octahedral
Bond angle – 90
Hexaaqua complexes
draw a 3D shape of a complex ion with a coordination number of 6
what are the shapes that arise from a coordination number of 4
tetrahedral and square planar
bond angle + example for tetrahedral
Bond angle – 109.5
Tetrachloro complexes
bond angle for square planar
90
which metals make square planar complexes over tetrahedral
tends to occur for transition metals with 8 d electrons
Platinum (II), palladium (II) and gold (III)
draw a tetrahedral complex
draw a square planar complex
what is a monodentate ligand
ligand that is able to donate one pair of electrons to a central metal atom
what is a bidentate ligand
able to donate 2 pairs of electrons to a central metal atom
what are 5 examples of monodentate ligands
examples of bidentate ligands
what complexes show cis-trans isomerism
4 coordinate + 6 coordinate complex ions with different monodentate / bidentate ligands
which complexes show both cis trans and optical isomerism
6 coordinate complexes with monodentate and bidentate ligands
what needs to be for a square planar complex to show cis trans isomerism
have no more than 2 identical ligands
cis square planar
two identical ligands are adjacent to eachother - 90 degrees apart
trans square planar
two identical ligands are opposite each other - 180 degrees apart
draw the cis + trans isomers of [Pd(NH3)2(Cl)2]
what needs to be for an octahedral monodentate complex to show cis trans isomerism
contain 4 of one type + 2 of another type of ligand
cis monodentate octahedral
two identical ligands are adjacent to each other - 90 degrees
trans monodentate octahedral
two identical ligands are opposite to each other - 180 degrees
draw the cis + trans isomers of [Co(NH3)4(Cl)2]+
what needs to be for an octahedral bidentate complex to show cis trans isomerism
contain 2 bidentate ligands + 2 identical monodentate ligands
cis bidentate octahedral
two identical monodentate ligands adjacent to each other - 90 degrees
trans bidentate octahedral
two identical monodentate ligands are opposite to each other - 180 degrees
draw cis + trans [Co(NH3CH2CH2NH2)2 (Cl)2]+
do square planar complexes show optical isomerism
no
do octahedral complexes show optical isomerism
yes
what needs to be for a octahedral complex to show optical isomerism
ONLY in cis isomers with 2 or more bidentate ligands
can trans octahedral show optical isomerism
no
can cis octahedral show optical isomerism
yes
draw the optical isomers of [Co(NH3CH2CH2NH2)2 (Cl)2]+
remember only cis
draw optical isomers of [Ni(NH3CH2CH2NH2)3]2+
what is ligand substitution
Where 1 ligand is exchanged for another
what does ligand substitution normally cause
colour change
what occurs when ligand exchange happens between two similar sized ligands
If ligands similar size – coordination number of complex ion or shape does not change
what are some examples of similar sized ligands
H2O
NH3
what colour is a solution of [Cr(H2O)6]3+
violet solution
write out the reaction between [Cr(H2O)6]3+ and NH3
describe the observations for the reaction between [Cr(H2O)6]3+ and NH3
colour change from a violet solution to a purple solution
does the shape of the metal complex change when you react [Cr(H2O)6]3+ and NH3
no - both octahedral as they are similar sized ligands
what colour is [Cr(NH3)6]3+
purple solution
what colour is [Cr(H2O)5SO4]+
green solution
write out the reaction between [Cr(H2O)5SO4]+ and NH3
describe the observations for the reaction between [Cr(H2O)5SO4]+ and NH3
colour change from green to purple
does the shape of the metal complex change when you react [Cr(H2O)5SO4]+ and NH3
no - both octahedral - as similar sized ligands
what are the products in the reaction between [Cr(H2O)5SO4]+ and NH3
does copper undergo ligand exchange
yes BUT only partial exchange
what colour is [Cu(H2O)6]2+
pale blue solution
write out the equation when [Cu(H2O)6]2+ reacts with ammonia
draw [Cu(H2O)6]2+
describe the observations for the reaction between [Cu(H2O)6]2+ and ammonia
pale blue to dark blue solution
does the shape of the metal complex change when you react [Cu(H2O)6]2+ and ammonia
no - both octahedral as they are similar sized ligands
what are the products in the reaction between [Cu(H2O)6]2+ and ammonia
draw [Cu(NH3)4(H2O)2]2+
what happens if a small uncharged swapped for large charged ligand (or vice versa)
change in shape + coordination number
write out the reaction between [Cu(H2O)6]2+ and chloride ions
describe the observations that occur when you react [Cu(H2O)6]2+ and chloride ions
pale blue to yellow
does the shape of the metal complex change when you react [Cu(H2O)6]2+ and chloride ions
yes - because Cl- are smaller
what is the shape change when you react [Cu(H2O)6]2+ and chloride ions
[Cu(H2O)6]2+ = tetrahedral
[Cu(Cl4)]2- = tetrahedral
where do the chloride ions come from in the reaction between [Cu(H2O)6]2+ and chloride ions
concentrated HCl
what are the products the reaction between [Cu(H2O)6]2+ and chloride ions
draw both [Cu(H2O)6]2+ and [Cu(Cl4)]2-
how does ammonia form hydroxide ions
NH3 + H2O ⇌ NH4+ + OH-
Why does the solution of aqueous copper (II) ions reacting with chloride ions turn green as the reaction proceeds?
The yellow and blue solutions mixing gives a green colour.
What is formed when chromium(III) potassium sulphate is dissolved in water?
what’s the formula and colour?
The complex ion [Cr(H2O)6]3+ is formed.
A pale purple solution.
What is formed instead when only chromium(III) sulphate is dissolved in water?
what’s the formula and colour?
The complex ion [Cr(H2O)5SO4]+ is formed.
A green solution.
what happens if ammonia / sodium hydroxide added to aqueous transition metal complexes dropwise
coloured precipitates of insoluble transition metal hydroxide forms
what is a precipitation reaction
two aqueous solutions that contain ions react together to form an insoluble ionic solid
are precipitation reactions reversible
yes
precipitates can be re-dissolved by adding acid
when you add ammonia / sodium hydroxide to these metal complexes what happens first
it will initially form the metal hydroxide
What colour is Fe2+
pale green solution
what are the observations when you add dropwise ammonia / sodium hydroxide to Fe2+
pale green solution to a green ppt (turns orange on standing)
what is the green ppt when you add dropwise ammonia / sodium hydroxide to Fe2+
Fe(OH)2
write out the reaction between dropwise ammonia / sodium hydroxide and Fe2+
why does Fe(OH)2 turn orange on standing
gets oxidised to Fe3+
what colour is Fe3+
pale yellow solution
what are the observations when you add dropwise ammonia / sodium hydroxide to Fe3+
pale yellow solution to orange brown ppt
what is the orange brown ppt
Fe(OH)3
write out the reaction between dropwise ammonia / sodium hydroxide and Fe2+
describe the observations when you react [Cu(H2O)6]2+ with dropwise ammonia vs excess ammonia
describe the observations when you react [Cr(H2O)6]3+ with dropwise ammonia vs excess ammonia
describe the observations when you react [Cr(H2O)6]3+ with dropwise sodium hydroxide vs excess sodium hydroxide
Describe the precipitation reaction of Fe2+ with OH and what is the equation?
Fe2+ + 2OH- = Fe(OH)2 (s)
pale green solution to green precipitate
Describe the precipitation reaction of Fe3+ with OH and what is the equation?
Fe3+ + 3OH- = Fe(OH)3 (s)
pale yellow to orange-brown precipitate
Describe the precipitation reaction of Mn2+ with OH and what is the equation?
Mn2+ + 2OH- = Mn (OH)2 (s)
pale pink solution to light brown precipitate
Describe the precipitation reaction of Cr3+ with OH and what is the equation?
Cr3+ (aq) + 3OH- (aq) = Cr(OH)3 (s)
violet solution to green precipitate
Describe the precipitation reaction of Cu2+ with NaOH and what is the equation?
Cu2+(aq)+2NaOH(aq)→ Cu(OH)2(s)+2Na+(aq)
pale blue solution to a blue precipitate of copper(II) hydroxide.
How do Cr3+ react with an excess of aqueous NaOH?
the hydroxide of Cr 3+ does dissolve in excess NaOH
Cr3+ + NaOH (aq)= Cr(OH)3 (s)
excess NaOH=[Cr (OH)6] 3-
Cu2+
appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH
Fe2+
appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH
Fe3+
appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH
Mn2+
appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH
Cr3+
appearance of aqueous solution
observations with dropwise NaOH / NH3
observations with excess NH3
observations with excess NaOH
what is haemoglobin
A metalloprotein
what is the structure of haemoglobin
Central Fe2+ metal ion
Multidentate haem ring = 4 nitrogen’s, forming 4 dative covalent bonds (in square planar configuration)
Also forms a dative bond with the protein globin
Finally, dative bond with O2 or H2O (ligands)
Coordination number 6, octahedral overall
how is oxyhaemoglobin
- Binds reversibly with oxygen via ligand exchange
how is the dative bond between oxygen and Fe2+ advantageous
as it releases O2 when needed
why is carbon monoxide dangerous
Carbon monoxide has a lone pair of electrons on its carbon – can act as a ligand
much stronger dative bond forms between CO and Fe2+ in the haem group than O2
Any CO breathed in, will permenantly replace O2, ligand exchange
Forms carboxyhaemoglobin
write out both equations of haemoglobin + oxygen / carbon monoxide
Haemoglobin + oxygen ⇌ oxyhaemoglobin
Haemoglobin + carbon monoxide → carboxyhaemoglobin
what colour is (MnO4)-
purple
colour change when fe3+ reacts with I-
orange brown Fe3+ reduced to pale green fe2+
pale green obscured by the oxidation of I- to I2 - brown colour
conditions for oxidation of Fe2+
H+/MnO4-
conditions for reduction of Fe3+
I–
write out equation for oxidation of fe2+ AND colour changes
write out the equation for the reduction of Fe3+ AND colour change
what colour are dichromate ions
orange
what colour are chromium (III) ions
green
conditions for reduction of dichromate ions
Zn/H+,
write out the equation for the reduction of dichromate ions AND colour change
what happens if an excess if zinc is added to dichromate ions
chromium 3+ ions reduced further to chromium 2+
what colour is chromium 2+
pale blue
write out the equation for the reduction of chromium in excess zinc AND colour change
conditions for oxidation of Cr3+
hot alkaline hydrogen peroxide
hydroxide ions
write out the equation of the oxidation of Cr3+
conditions for reduction of Cu2+
I- (excess)
write out the equation for reduction of Cu2+ AND colour change
what happens in aqueous conditions for copper
Cu+ readily disproportionates.
compound where Cu has oxidation state 1
Cu2O - copper oxide
example of disproportionation of Cu+ ions
Copper oxide reacts with hot dilute sulfuric acid
