5.3 Transition Elements (completed) Flashcards
What is the definition of a transition element?
D-Block element that form one or more stable ions with partially filled d sub shells
What is different about the electronic configuration of chromium and copper?
They promote electrons from the 4s sub shell to the 3d sub shell in order to make it more stable
Why are zinc and scandium considered not transition metals?
They don’t form stable ions with an incomplete d sub shell
What colour are the two chromium ions you need to know?
Cr 3+ Green
Cr 6+ Orange
What colour are the two manganese ions you need to know?
Mn 2+ Pink
Mn 7+ Purple
What colour are the two iron ions you need to know?
Fe 2+ Green
Fe 3+ Orange
What colour is the copper ion you need to know?
Cu 2+ Blue
How do transistion metals catalyse reactions?
Adsorption – gases are pulled onto the surface of catalyst
Bonds weakening and reaction takes place
Desorption – products leave surface of catalyst
What do transition metal hydroxide tend to be?
Insoluble so a solid precipitate can form with a certain colour
What are the colours of the following hydroxide precipitates? Cu 2+ Cr 3+ Fe 2+ Fe 3+ Mn 2+
Cu(OH)2 Light blue Cr (OH)3 Dark green Fe (OH)2 Dark Green Fe (OH)3 Orange-brown Mn (OH)2 Brown
What is a complex ion?
A central metal ion surrounded by ligands
What are ligands?
Species that can donate one more lone pairs of electrons to form dative bonds with a central ion
What is the coordination number?
The number of dative bond is formed in a complex ion
Name three ligands?
Water
Ammonia
Cl-
What is the definition of monodentate, bi dentate and multidentate?
Can donate one lone pair H2O NH3 Cl- Can donate two lone pairs NH2CH2CH2NH2 en Can donate three or more lone pairs EDTA4- (6 lone pairs)
What are the three structures of complex ions?
Tetrahedral – four bonding pairs 109.5°
Octahedral – six bonding pairs 90°
Square planar – four bonding pairs 90°
What is cisplatin?
[PtCl2(NH3)2] Square planer Two stereo isomers (cis, trans) Cis used as an anti-cancer drug Trans isomer has no anti-cancer properties
What are optical isomers?
Isomers that a non-super imposible mirror images of each other
Why is haemoglobin a complex ion?
In each haem group there four nitrogen atoms that form co ordinate bonds with Fe 2+ ion
What is the ligand substitution of Chromium (III) with NaOH?
Purple Solution [Cr(H2O)6]3+
Add NaOH solution
Light Green Precipitate Cr(OH)3 firmed
Add excess NaOH solution
Dark green solution [Cr(OH)6]3-
Why does [Cr(H2O)6]3+ not often appear as a purple solution?
A tiny amount of impurity will turn the solution green
What happens if you add excess ammonia to a Chromium (III) Hydroxide?
Light green precipitate → Purple Solution
[Cr(NH3)6]3+
What is the ligand substitution of Copper (II) with HCl?
Blue solution [Cu(H2O)6]2+
Add excess concentrated HCl
Yellow solution [CuCl4]2-
(green initially)
Add excesss H2O returned to
Blue solution [Cu(H2O)6]2+
What is the ligand substitution of Copper (II) with ammonia?
Light Blue solution [Cu(H2O)6]2+
Add excess concentrated NH3
Dark Blue solution [CuCl4]2-
Initially a small amount of a light blue precipitate of copper hydroxide but then in excess this dissolves
Add excesss H2O returned to
Light Blue solution [Cu(H2O)6]2+
What is the colour change of the oxidation of Fe2+ and Cr2O7 2-?
Fe2+ → Fe3+
Light green → Red/Brown
Cr2O7 2- → Cr3+
Orange → Green
What are the properties of transition metals?
Variable oxidation states
Form colour compounds
Can act as a catlyst
Form insoluble hydroxide precipitates
What types of catalysts are transition metals?
Usually heterogenous catalysts
Catalyse reactions in a different phase to themselves
e.g. solid iron catalysing gaseous haber process
What catalyses the Haber Process?
Iron
How does oxygen and carbon monoxide bind to haemoglobin?
Oxygen binds reversibly to the Fe2+ ion in the haem group
Cyanide ions and carbon monoxide bind more strongly
What is the colour change of the reduction of Cu 2+ ions?
Cu2+ → Cu+
Blue → Colourless
Why is Cu + colourless?
It does not have an incomplete d sub shell
What is the disproportionation of Cu +?
Cu+ → Cu(s) + Cu2+
Explain using ligand substitutions how haemoglobin transports oxygen and why CO is toxic?
O2 forms dative bonds with iron
Ligand substitution occurs and O2 is replaced by H2O or CO2 when needed for transport
CO forms stronger bonds with iron than O2
What is the colour of CoCl4 2- and how is it formed?
Dark blue
From CoCl2.6H2O(s) plus water and excess HCl
What is the colour of CrO4 2- and how is it formed?
Oxidation of Cr3+ with hot alkaline H2O2
yellow
What is the colour of Mn(OH)2 and how is it formed?
NaOH dropwise to [Mn(H2O)6]
2+ pale brown precipitate
From light pink solution
What is the colour of [Fe(H2O)6] 2+ and how is it formed?
From FeSO4.7H2O(s)
pale green
What is the colour of Fe(OH)2 (s) and how is it formed?
NaOH dropwise to Fe2+(aq)
dark green precipitate
What is the colour of [Fe(H2O)6] 3+ and how is it formed?
From FeCl3.6H2O(s)
yellow
What is the colour of Fe(OH)3 (s) and how is it formed?
NaOH dropwise to Fe3+(aq)
orange-brown precipitate
What is the colour change of the titration of MnO4/Fe2+ to Mn2+/Fe3+?
purple (MnO4) to pale pink (Mn2+)
in titrations, so dilute that it is practically colourless
What is the colour change of the titration of I/Fe3+ I2/Fe2+
orange brown (Fe3+) to brown (I2)
