✅15 - Transition Metals Flashcards
Where are transition metals found in the periodic table?
D block
What are transition metals?
D block elements that can form one or more stable ions with incompletely filled d-orbitals
Which d block period 4 elements are not transition metals?
Scandium and Zinc
How many electrons can the d orbital hold?
10
When ions are formed, which electrons are removed first?
The s electrons
Why is Scandium not a transition metal?
It only forms one ion, Sc3+, which has an empty d subshell
Why is zinc not a transition metal?
It only forms one ion, Zn2+, which has a full d subshell
How many stable oxidation states does Vanadium have?
4
What are the stable oxidation states of Vanadium?
II, III, IV, V
What do transition metals have?
Variable oxidation states
What conditions must be met to form a compound of complex with an ion of a certain oxidation number?
The energy given out when the ion forms a compound or complex needs to be greater than the ionisation energy
How do transition metals form ions?
By loosing electrons from their 4s and 3d subshells
When does the energy released when an ion forms a complex or compound increase?
When the ionic charge increases.
What are complex ions?
Metal ions surrounded by datively covalently bonded ligands
What is a ligand?
An atom, ion or molecule which donates a pair of electrons to a central metal atom or ion.
What are monodentate ligands?
Ligands with one lone pair
What are bidentate ligands?
Ligands with two lone pairs
What are multidentate ligands?
Ligands with more than two lone pairs
What are examples of monodentate ligands?
H2O, NH3, Cl-
What is an example of a multidentate ligands?
EDTA 4-
What is the name for water in a complex?
Aqua
What is the name for a hydroide group in a complex?
hydroxo
What is the name for ammonia in a complex?
Ammine
What is the name for chloride in a complex?
Chloro
How many colours traditionally make up white light?
7
Why are transition metal complexes coloured?
Electrons split into two energy levels when ligands attach. If an electron absorbs light, it can move to a higher energy level, and the light reflected is the colour seen
With 6 ligands, what shape is a complex?
Octahedral
With 4 ligands, what shape is a complex?
Tetrahedral or square planar
With 2 ligands, what shape is a complex?
Linear
What is an example of a linear complex?
Tollen’s reagent
What is cis-platin?
An anti-cancer drug which has a square planar shape
What does a cis- prefix indicate?
That the identical ligands are next to each other
What does a trans- prefix indicate?
That the identical ligands are opposite each other
Why does reducing the number of ligands increase stability?
The system becomes more disordered and there is an increase in ∆S system
What causes the greatest increase in stability?
Exchanging a monodentate ligand for a multidentate ligand
What is the equation for the reaction between aqueous NaOH and copper(II) sulfate solution?
[Cu(H2O)6]2+ + 2OH- —> [Cu(H2O)4(OH)2] + H2O
What colour is [Cu(H2O)4(OH)2]?
Blue precipitate
What is the equation for the reaction between aqueous ammonia and copper (II) sulfate?
[Cu(H2O)6]2+ + NH3 —-> [Cu(H2O)4(OH)2] + 2NH4+
What is the equation for the reaction between the blue copper precipitate and aqueous ammonia?
[Cu(H2O)4(OH)2] + 4NH3 —-> [Cu(NH3)4(H2O)2]2+ + 2H2O + 2OH-
What colour is [Cu(NH3)4(H2O)2]2+?
Deep blue solution
What is the equation for the reaction between copper (II) sulfate solution and conc HCl?
{CU(H2O)6]2+ + 4Cl —-> [CuCl4]2- + 6H2O
What is the colour change when hydrochloric acid is added to copper sulfate solution?
Blue to green to yellow
What is the equation for the reaction between hexaaquacobalt(II) and aqueous sodium hydroxide?
[Co(H2O)6]2+ + 2OH- —-> [Co(H2O)4(OH)2] + 2H2O
What is the colour change when sodium hydroxide is added to hexaaquacobalt(II)?
Pink solution to blue precipitate
How many reactions occur between hexaaquacobalt(II) and ammonia?
2
What is the acid-base reaction between hexaaquacobalt(II) and NH3?
[Co(H2O)6]2+ + 2NH3 —-> [Co(H2O)4(OH)2] + 2NH4+
What is the equation for the reaction between [Co(H2O)4(OH)2] and NH3?
[Co(H2O)4(OH)2] + 6NH3 —-> [Co(NH3)6]2+ + 4H2O + 2OH-
What is the colour change between hexaaquacobalt(II) and ammonia?
Precipitate dissolves to a brown solution
What is the colour od the [Co(NH3)6]3+ ion?
Yellow
What is the equation for the reaction between hexaaquacobalt(II) and conc HCl?
[Co(H2O)6]2+ + 4Cl- —-> [CoCl4]2- + 6H2O
What is the colour change when conc HCl is added to the hexaaquacobalt (II) solution?
Pink to blue
What is the equation for the reaction between hexaaquairon(II) and sodium hydroxide?
[Fe(H2O)6]2+ + 2OH- —-> [Fe(H2O)4(OH)2] + 2H2O
What is the colour change in the reaction between hexaaquairon(II) and sodium hydroxide?
Pale green solution forms a green precipitate
What is the equation for the reaction between hexaaquairon(II) and NH3?
[Fe(H2O)6]2+ + 2NH3 —-> [Fe(H2O)4(OH)2] + 2NH4+
What is the equation for the reaction between hexaaquairon(III) and sodium hydroxide?
[Fe(H2O)6]3+ + 3OH- —-> [Fe(H2O)3(OH)3] + 3H2O
What is the colour change for the reaction between hexaaquairon(III) and sodium hydroxide?
Yellow-brown solution forms and brown precipitate
What is the equation for the reaction between hexaaquairon(III) and NH3?
[Fe(H2O)6] + 3NH3 —-> [Fe(H2O)3(OH)3] + 3NH4
What are the colours shown by chromium compounds affected by?
Some compounds have different colours as solids and aqueous solutions
The colour of the solution depends on the concentration
The presence of dissolved oxygen in an aqueous solution can affect the colour seen
What is the equation for the reaction between the hexaaquachromium(III) ion and aqueous sodium hydroxide?
[Cr(H2O)6]3+ + 3OH- —-> [Cr(H2O)3(OH)3] + 3H2O
What is the colour change for the reaction between hexaaquachromium(III) and sodium hydroxide?
Green or violet solutions forms a green precipitate
What is the equation for the reaction between hexaaquachromium(III) and NH3?
[Cr(H2O)6]3+ + 3NH3 —-> [Cr(H2O)3(OH)3] + 3NH4+
What happens to the precipitate [Cr(H2O)3(OH)3] when it is dissolved?
It dissolves to form a green solution of [Cr(H2O)2(OH)4]-
What happens to the precipitate [Cr(H2O)3(OH)3] when excess ammonia is added?
It is slow to dissolve but eventually a violet or purple solution of [Cr(NH3)6]3+ forms
What is the equation for the reaction between [Cr(OH)6]3- and hydrogen peroxide?
2[Cr(OH)6]3- + 3H2O2 —-> 2CrO42- + 2OH- + 8H2O
What is the colour change for the reaction between the chromium complex and hydrogen peroxide?
Green solution to yellow solution
What is hydrogen peroxide?
An oxidising agent
How does the chromate ion change with acidity?
In alkaline solution, the chromate(VI) ions are stable, but in acidic solution the dichromate(VI) are most stable
What colour change is seen if acid is added to chromate ions?
Yellow to orange
What can dichromate(VI) ions be reduced by?
Zinc
What is the equation for the reduction of dichromate ions using zinc?
Cr2O72- + 14H+ +3Zn —-> 2Cr3+ + 7H2O + 3Zn2+
What is the colour change when dichromate ions are reduced?
Orange to green
What is the colour change when Cr3+ is reduced to Cr2+?
Green to blue
What reaction happens when NaOH is added to [Cr(H2O)3(OH)3]?
It forms [Cr(OH)6]3-
What colour are V2+ ions?
Purple
What colour are V3+ ions?
Green
What colour are (VO)2+ ions?
Blue
What colour are (VO2)+ ions?
Yellow
In what compound does vanadium have a +4 oxidation number?
(VO)2+
In what compound does vanadium have a +5 oxidation number?
(VO2)+
Why is it easy to demonstrate a change in oxidation number with vanadium?
Because its colour changes are so distinctive
What can be used to reduce vanadium from +5 to +2?
Zinc
What is the equation for the reduction of vanadium from +5 to +4?
2(VO2)+ + 4H+ + Zn —-> 2(VO)2+ + Zn2+ + 2H2O
What is the equation for the reduction of vanadium from +4 to +3?
2(VO)2+ + 4H+ + Zn —-> 2V3+ + Zn2+ + 2H2O
What is the equation for the reduction of vanadium from +3 to +2?
2V3+ + Zn —-> 2V2+ + Zn2+
What is the equation for the reduction of vanadium from +2 to 0?
2V2+ + Zn —-> 2V + Zn2+
Which of the vanadium reductions is not thermodynamically feasible?
+2 to 0
What is the equation for the reaction between persulfate ions and iodide ions?
S2O82- + 2I- —-> 2SO42- + I2
What is the catalyst in the reaction between iodide and persulfate ions?
Fe2+
What are the steps in the reaction between I- and S2O82-?
S2O82- and 2Fe2+ react together to form 2SO42- and 2Fe3+
2Fe3+ react with 2I- to form 2Fe2+ and I2
Why do the Fe2+ and S2O82- react together?
Because they do not repel each other, as they have the opposite charge
What is the alternative mechanism for the reaction between I- and S2O82-?
2Fe3+ + 2I- —-> 2Fe2+ + I2
S2O82- + 2Fe2+ —-> 2SO42- + 2Fe3+