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Chemistry Module 5 > transition metals > Flashcards

transition metals Flashcards

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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

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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
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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
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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
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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
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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
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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
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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,
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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)

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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
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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
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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
Q

what happens n a bidentate ligand

A
  • 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
Q

name some neutral ligand

A
  • OH2

- NH3

27
Q

name the negative ligands

A
  • SCN-
  • CN-
  • Cl-
  • OH-
28
Q

what is the uses of EDTA

A
  • 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
Q

what is a mutlidentate ligand

A
  • a hexadentate ligand has six lone pairs of electrons avaliable to form coordiante bonds
30
Q

describe EDTA and draw it

A
  • 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
Q

describe the octahedral shape of a complex ion

A
  • 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
Q

draw [Co(H2O)6]2+

A

draw it

33
Q

draw the 3d octahedral shape

A

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
Q

describe octahedral complexes with mutlidentate ligands

A
  • 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
Q

describe chloride ions as ligands

A
  • chloride ligands are so large that only 4 can fit around a transition metal ion so chlroide complexes form a tetrahedral shape
36
Q

what are square planar complex

A
  • 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
Q

what is cis platin

A
  • cis plantin is the cis-isomer of a plantinum complex [PtCl2(NH3)2]
  • square planar
  • effective against cancer
38
Q

what is a stereoisomer

A

this is species with the same structural formula but with a different arrangement of the atoms in space

39
Q

what are the two types of steroisomeism transition element

A
  • cis-trans

- optical

40
Q

what are the two different octahedral complex ions ligands

A
  • four monodentate ligands and two different monodentate ligands
  • two bidentate ligands and two different bidentate ligands
  • these exist as cis and trans isomers
41
Q

describe early examples of steroisomerism

A
  • early examples of sterioisomerism involves Co3+ complex ions
  • Sophus Mads Jorgensen observed that some complex ions could form salts that had different colours
42
Q

who succeeded in explaining the existence of two isomers

A
  • 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
Q

what other shape is cis trans isomerism possible in

A
  • 4 coordinate complexes - square planar shape

- the complex must contain two different ligands with two of one ligand and two of another

44
Q

How does cis platin work

A
  • 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
Q

whats the negatives of cis platin

A
  • severe sickness
  • hair loss
  • fatigue
46
Q

if they are close together then they are

A

cis

47
Q

if they are far apart than they are

A

trans

48
Q

what are the requirements for optical isomerism

A
  • 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
Q

describe optical isomers

A
  • 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
Q

whats a racemic mixture

A
  • this is a mixture containing equal amounts of two optical isomers and has no effect on plane-polarised light because the rotations cancel out

Chemistry Module 5 (11 decks)

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