Chapter 24 - Transition Elements Flashcards
D-block element, The formation and shapes of complex ions, Stereoisomerism in complex ions, Ligand substitution and precipitation, Redox and qualitative analysis.
What are the two irregularities in the d-block in terms of electron configuration?
Chromium: 3d5 4s1 instead of 3d4 4s2
Copper: 3d10 4s1 instead of 3d9 4s2
Why do these irregularities exist in the d block electron configurations?
A half filled and a fully filled d sub shell gives greater stability to these atoms.
What are transition elements?
D-block elements that form at least one ion with a partially filled d-orbital.
Which d-block elements are excluded from being transition elements?
Scandium and zinc
What are the properties of the transition elements?
Form compounds in which the transition element has different oxidation states
Form coloured compounds
Elements and compounds can act as catalysts
What colours are the various ions of Chromium?
+3 green
+6 orange
What colours are the various ions of Copper?
+2 blue
What colour is potassium dichromate(VI)?
Orange
What colour is cobalt(II) chloride?
Pink-purple
What colour is nickel(II) sulfate?
Green
What colour is hydrated copper(II) sulfate?
Blue
What is the catalyst used in the Haber process?
Iron
What is the catalyst used in the Contact process?
Vanadium(V) oxide
V2O5
What is the catalyst used in hydrogenation?
Nickel
What is the catalyst used in catalytic decomposition of hydrogen peroxide?
Manganese(IV) oxide
MnO2
Define what a complex ion is
A transition metal ion bonded to ligands by coordinate bonds.
Define coordination number
The number of coordinate bonds attached to the central metal ion.
Define what a ligand is
A molecule or ion that can donate a pair of electrons to the transition metal ion to form a coordinate bond.
What is meant by a monodentate ligand?
A ligand that is able to donate one pair of electrons to a central metal ion.
Give 6 examples of common monodentate ligands and their charges
Water H2O neutral Ammonia NH3 neutral Thiocyanate SCN- -1 Cyanide CN- -1 Chloride Cl- -1 Hydroxide OH- -1
What shape is created from a complex ion having a coordination number of 6?
Octahedral
What shapes can be created from a complex ion having a coordination number of 4?
Tetrahedral
OR
Square planar
When is a square planar shape formed in a complex ion?
When the transition metal in the complex ion has eight d-electrons in the highest energy d-sub-shell.
What is stereoisomerism?
Same structural formula but a different arrangement of the atoms in space.
What are the two types of stereoisomerism?
Cis-trans isomerism
Optical isomerism
When can complex ions show cis-trans isomerism?
Four or six coordinate complex ions with two different monodentate ligands.
When can complex ions show both types of stereoisomerism?
Six coordinate complex ions containing monodentate and bidentate ligands.
What is optical isomerism?
Non-superimposable mirror images of each other.
Called enantiomers
Define ligand substitution
One ligand in a complex ion is replaced by another ligand.
Describe ligand substitution of aqueous copper(II) ions with ammonia
Four of the waters are replaced by ammonia ligands, the solution turns from pale blue to dark blue.
Describe ligand substitution of aqueous copper(II) ions with chloride ions
The six water ligands are replaced by four chloride ion ligands. The solution starts out pale blue and moves to yellow on completion.
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.
Why does the shape of the aqueous copper (II) ion change from octahedral to tetrahedral when it reacts with chloride ions?
Chloride ligands are larger in size than water ligands so fewer of them can fit around the Cu2+ ion.
What is formed when chromium(III) potassium sulphate is dissolved in water?
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?
The complex ion [Cr(H2O)5SO4]+ is formed.
A green solution.
Describe the reaction between [Cr(H2O)6]3+ and an excess of aqueous ammonia
A grey green precipitate of Cr(OH)3 is formed initially.
Cr(OH)3 dissolves in excess ammonia to form the complex ion [Cr(NH3)6]3+.
A purple solution.
How does ligand substitution help with gas exchange in blood?
In haemoglobins there is a central Fe2+ ion that can bind to oxygen gas.
The oxygen is released to cells and carbon dioxide can bond to the Fe2+ where it is released in the lungs.
What is a precipitation reaction?
Two aqueous solutions containg ions react together to form an insoluble ionic solid.
Describe the precipitation reaction of Cu2+ with NaOH
Blue solution reacts to form a blue precipitate of copper(II) hydroxide.
Insoluble in excess NaOH.
How do Fe2+, Fe3+ and Mn2+ react with an excess of aqueous ammonia?
Same way as they react with NaOH.
Form hydroxide precipitates.
Insoluble in excess ammonia.
uses of silver, nickel l, zinc
jewellery, coins
uses of iron
steel also as a catalyst in the harbor process
Uses of copper
wires, pipes
Uses of titanium
uses in aerospace industry due to high strength, joint replacement and cosmetic dentistry
No charge on complex makes it
It makes it insoluble in solution
