1
Q
what is a transition metal
A
a transition element is a d-block element that has an incomplete d-sub-shell as a stable ion
2
Q
why are scandium and zinc not transition metals
A
scandium and zinc are the first and last members of the period 4 d-block elements and are not classed as transition metals because they do not have any ions partially filled d-orbitals
- scandium forms only Sc3+ ion in which the d-orbitals are empty
- zinc only forms the Zn2+ ion which the d-orbitals are full
3
Q
transition element electronic configuration rules
A
- the sub shell energy levels in the third and fourth energy levels overlap
- the 4S sub shell fills before the 3d sub shell
4
Q
describe when the electronic configuration pattern breaks
A
- breaks for chromium and copper, in order to reduce the electron repulsion between the outer electrons resulting in increased stability for the copper and chromium atoms
- chromium - the 5 3d orbitals and 4s orbitals all contain one electrons with no orbital being completely filled
- cooper the 5d orbitals are filled but there is only one electron in the 4s orbital
5
Q
what happens in reactions of transition elements
A
- in the reactions transition element atoms lose electrons to form positive ions
- they lose their 4s electrons before there 3d electrons
- this is because the 3d and 4s energy levels are close together and once electrons occupy the orbitals the 4s electrons have a higher energy and are lost first
6
Q
what are the physical properties of transition metal compounds
A
- transition elements are all metals,
- high densities
- high melting and boiling points
- exist as giant metallic lattices
- contain delocalised electrons so can conduct electricity
7
Q
what are the chemical properties
A
- they have different oxidation states
- transition metals form coloured solutions when dissolved in water
- catalyse chemical reactions - due to partially filled d-orbitals
8
Q
describe the variable oxidation states for transition elements
A
- the transition elements from titanium to copper all form ions with more than one stable oxidation state
- these metals also all form compounds with metal ions in the +2 oxidation state, this results from loosing two electrons in the 4s orbital
- the highest oxidation state of a transition element is found in a strong oxidising agent,
9
Q
describe coloured compounds
A
- when white light passes through a solution containign transition metal ions some of the wavelengths of visible light are absorbed, the colour that we observe is a mixture of the wavelengths of light that have not been absorbed
- for example a solution of copper sulfate appears pale blue becasue the solution absorbs the red/orange region of the electromagnetic spectrum and reflects or transmits the blue
- colour is linked to the partially filled d-orbitals of transition metal ions
10
Q
why does scandium(III) not have a coloured compound
A
- scandium does not have d shell and is colourless in aqueous solution, scandium III is formed from scandium by the loss of 2 4s electrons and one 3d electron there is no partially filled d-orbital and there is no colour
11
Q
describe how transition metals act as catalysts
A
- they provide a surface on which a reaction can take place, reactants are adsorbed onto the surface of the metal and held in place while a reaction occurs, after the reaction the products are desorbed an d the metals remain unchanged
- transition metal ions have the ability to change their oxidation states by gaining or losing electrons, they bind to reactants forming intermediates as part of a chemical pathway often with a lower activation energy which speeds up the reaction
12
Q
describe transition metals as industrial catalysts
A
- transition metal catalysts are used in industry to improve the profits of an industrial process, they can reduce the time it takes to make a product and reduce the amount of energy needed to make the reaction occur
- toxic
- when substances bind to the active site and stop the transition metal catalysts from working the catalysts can no longer be used, must be disposed of in a way that does not cause harm or pollution
13
Q
describe haber process
A
- used to make ammonia from the reaction of nitrogen and hydrogen
- catalyst is an iron metal - used to increase the rate of reaction and to lower the temperature at which the reaction takes place
- much of the ammonia produced in the Haber process is used in manufacturing agricultural fertilisers
14
Q
describe the contact process
A
- used to convert sulfur dioxide into sulfur trioxide which is used to manufacture sulfuric acid
- 2SO2 + O2 = 2SO3
- vanadium oxide in which vandium has the +5 oxidation state
- sulphuric acid is an important inorganic chemical with many uses including the production of fertilisers, detergents, adhesives and explosives and also as the electrolyte in car batteries
15
Q
describe the hydrogenation of alkenes
A
- hydrogen can be added across the C=C double bond in unsaturated compounds
- nickel metal - it is used to lower the temperature and pressure needed to carry out the reaction
- process is used in the hydrogenation of unsaturated vegetable oils to make spreadable margarines
16
Q
decomposition of hydrogen peroxide
A
- hydrogen peroxide decomposes slowly at room temperature and pressure into water and oxygen
- catalyst is added to increase the reaction rate
- 2H2O2 = 2H20 + O2
- manganese (IV) oxide MnO2, this is when manganese has the +4 oxidation state
- often called manganese dioxide
- used in laboratory as a simple way of making oxygen gas
17
Q
describe hydrogen production
A
- zinc granules will react with dilute sulfuric acid to form hydrogen and zinc sulfate
- when copper(II) sulfate is added the rate of reaction increases
- transition metal ion acts as a catalyst
- Zn + H2SO4 = ZnSO4 + H2
- reaction used to produce hydrogen gas
18
Q
what is a complex ion
A
this is a transition metal ion bonded to one or more ligands coordinate bonds (dative covalent bonds)
19
Q
what is a ligand
A
- this is a molecule or ion that can doante a pair of electrons to the transition metal ion to form a coordinate bond
20
Q
what is a coordination number
A
- this is the total number of coordinate bonds formed between a central metal ion and its ligands
21
Q
what does a transition metal do to accept a ligand
A
- it accepts the pair of electrons from the ligand and forms the coordinate bond
22
Q
in the formula of a complex ion…
A
- the square brackets group together the species making up the complex ion
- the overall charge is shown outside the brackets
23
Q
the overall charge is ….
A
the sum of the individual charges of the transition metal ion and those of ligands present in the complex
24
Q
what happens in a monodentate ligand
A
- the ligand donates just one pair of electrons to the central metal ion to form one coordinate bond
25
what happens n a bidentate ligand
- bidentate ligands have two pair of electrons from different atoms to donate to the central metal, therefore two coordinate bonds can be formed
- NH2CH2CH2NH2 - usually shortened to en
- each nitrogen atom donates its lone pair to the metal ion
26
name some neutral ligand
- OH2
| - NH3
27
name the negative ligands
- SCN-
- CN-
- Cl-
- OH-
28
what is the uses of EDTA
- in detergents - binds to calcium and magnesium ions to reduce hardness in water
- in some foods - as a stabiliser to remove metal ions that might catalyse the oxidation of the product
- in medical applications - it is added to blood samples to prevent clotting and used to treat patients suffering from lead and mercury poisoning
29
what is a mutlidentate ligand
- a hexadentate ligand has six lone pairs of electrons avaliable to form coordiante bonds
30
describe EDTA and draw it
- hexadentate lignad
- exosts in complexes as the ion EDTA 4-
- EDTA is used to bind metal ions and is known as chelating agent, this means that EDTA decreases the concentration of metal ions in solutions by binding them into a complex
31
describe the octahedral shape of a complex ion
- has 6 coordinate bonds attached to the central ion
- the outer face of the shape is an eight sided octahedron, 4 of the ligands are on the same plane, one ligand is above the plane and the remaining are blow the plane - has the bond angles 90 or 180
32
draw [Co(H2O)6]2+
draw it
33
draw the 3d octahedral shape
draw it
- the solid wedge bonds come out of the plane of the paper towards you
- the hatched wedge bonds go into the plane of the paper away from you
- the ligands attached by the wedge bondsa re at teh corners of a sqaure with each bond separated by 90 degrees
- the solid lines represent bonds in the plane of the paper
- the oslid bonds are separated by wedge bonds by 90 degrees
34
describe octahedral complexes with mutlidentate ligands
- each en ligand forms two coordinate bonds to the central metal ion
- there are three en ligands giving a total of 3x2 = 6 coordiante bonds
- the coordination number is 6
35
describe chloride ions as ligands
- chloride ligands are so large that only 4 can fit around a transition metal ion so chlroide complexes form a tetrahedral shape
36
what are square planar complex
- a rare configuration is a square planar complex, this is when the four monodentate ligands arrnage themselves in the same plane as the metal atom
37
what is cis platin
- cis plantin is the cis-isomer of a plantinum complex [PtCl2(NH3)2]
- square planar
- effective against cancer
38
what is a stereoisomer
this is species with the same structural formula but with a different arrangement of the atoms in space
39
what are the two types of steroisomeism transition element
- cis-trans
| - optical
40
what are the two different octahedral complex ions ligands
- four monodentate ligands and two different monodentate ligands
- two bidentate ligands and two different bidentate ligands
- these exist as cis and trans isomers
41
describe early examples of steroisomerism
- early examples of sterioisomerism involves Co3+ complex ions
- Sophus Mads Jorgensen observed that some complex ions could form salts that had different colours
42
who succeeded in explaining the existence of two isomers
- Alfred werner
- werner propsed that there were two isomers of [Co(NH3)4Cl2]+
- one was purple and one was green
- he suggested that the cobalt (III) ion was surrounded by 4 NH3 ligands and 2Cl- ligands at the corners of an octahedron
he called the purple isomer cis
- the two Cl- ligands are at adjacent corners of the octahedron
- the two Cl- ligands are at 90 degrees to one another
he called the gren isomer trans
- the two Cl- ligands are at opposite corners of the octahedron
- the two Cl- ligands are at 180 to each other
43
what other shape is cis trans isomerism possible in
- 4 coordinate complexes - square planar shape
| - the complex must contain two different ligands with two of one ligand and two of another
44
How does cis platin work
- it acts by binding to the DNA of fast gorwing cancer, preventing cell division and prevents the cells from reproducing by changes to the DNA strucutre
- activation of cells own repair mechanism leads to death of cancer containing cells
- used in chemotherapy
- now developing a new generation of compounds with lower doses and fewer side effects such as carboplatin which treats ovarian cancer by slowing down cancer growth by reacting with a cells DNA
45
whats the negatives of cis platin
- severe sickness
- hair loss
- fatigue
46
if they are close together then they are
cis
47
if they are far apart than they are
trans
48
what are the requirements for optical isomerism
- a complex with three molecules or ions of a bidentate ligand
- a complex with two molecules or ions of a bidentate ligand and two molecules or ions of a monodentate ligand
- a complex with one hexadentate ligand
49
describe optical isomers
- they are non superimposable mirror images of each other
- they rotate plane-polarised light differently, one of the isomers rotates the light clockwise and the other anticlockwise
50
whats a racemic mixture
- this is a mixture containing equal amounts of two optical isomers and has no effect on plane-polarised light because the rotations cancel out
