Module 5.3.1- Transition metals

• d-block elements


  Groups 3-12 transition metals (in this topic we are looking only at period 4)
• energy levels for electrons in the d-block elements

  3d subshell has a higher energy level than the 4s hence 4s subshell fills up first (except for some exceptions)

  
• Why are chromium and copper exceptions to the regular arrangement of electrons of transition metals (4s not filling up first)

  This is because the 3d 5 subshell (half-filled) and 3d 10 (filled) subshell are more stable adding stability to the atoms (rather than 4s being filled up first)

  
• Electron configuration of d-block ions

  4s shell fills up first and empties first

  First in and first out

  
• Transition element


  A d-block element that forms an ion with apartially filled d sub-shell.
• Which elements do


  not match the transition element definition (A d-block element that forms an ion with an incomplete d sub-shell)

  Scandium since there are no electrons in the 3d subshell when it forms an ion (Sc3+)

  Normal: 1s2 2s2 2p6 3s2 3p6 3d1 4s2 Ion: 1s2 2s2 2p6 3s2 3p6

  Zinc since the 3d subshell is full when it forms an ion (Zn2+)

  Normal: 1s2 2s2 2p6 3s2 3p6 3d10 4s2Ion: 1s2 2s2 2p6 3s2 3p6 3d10
• Properties of transition metals and their compounds

  -form compounds in which transition metal has different oxidation states

  -form coloured compounds

  -elements and their compounds act as catalysts
• Variable oxidation states


  transition metals exist in more than one oxidation state e.g. Fe(II)X or Fe(III)X

  number of oxidation state increases across the transition elements to series to Manganese and then decreases

  
• Formation of coloured compounds


  Linked to partially filled d orbital of the transition metal ion

  Colour of solution can vary with oxidation state

  
• Transition metals as catalyst

  a catalyst works by providing an alternative reaction pathway with lower activation energy

  e.g. Fe in the The Haber process

  V2 O5 in The Contact process

  Ni in the hydrogenation of alkene

  Fe2+ in the reaction of iodide ions and peroxodisulfate ions where Fe2+ is regenerated(homogenous)
• Name the catalyst used for the reaction of


  Zinc with Acids Cu2+
• Name the catalyst used for the decomposition of

  H2O2(hydrogen peroxide)MnO2
• Complex ions


  formed when one or more molecules or negatively charged ions bond to a central metal ion
• Ligands


  coordinate (dative covalent) bonding to a metal ion or metal, including bidentate ligands
• Dative covalent bond (revision)


  A shared pair of electrons which has been provided by one of the bonding atoms only
• Coordination number indicates...


  ...the number of coordinate bonds attached to the central metal ions
• Representing complex ions

  ligand is inside round brackets e.g. (H2O)

  square brackets around whole molecule

  
  

  charge = sum of charges on central metal ion and any ligands present

  coordination number= 6 (in the pictured example)

  
• Monodentate ligands


  a ligand that is able to donate one pair of electrons to a central metal ion

  
• Bidentate ligands


  a ligand that is able to donate two pairs of electrons to a central metal ion forming two coordinate bonds

  
• Shape(s) of a 6-coordinate complex ion

  octahedral bond angles 90 degrees e.g. [Mn(H2O)6]2+

  
• Shape(s) of a 4-coordinate complex ion

  tetrahedral-109.5 degrees

  square planar-90 degrees (occurs due to 8 d-electrons in highest energy d sub-shell e.g. platinum (II), palladium(II) and gold(III) )

  
• What 2 types of stereoisomerism do complex ions display


  cis-trans isomerism and optical isomerism
• cis-trans isomerism in complex ions

  no double bond shape of complex holds groups in different orientations about the central metal ion

  some 4-coordinate/6-coordinate complex ions containing 2 monodentate ligands show cis-trans isomerism

  some 6-coordinate complex ions containing monodentate/bidentate ligands show both cis-trans and optical isomerism
• cis-trans isomerism in square planar complexes

  cis isomer - two identical groups adjacent to each other 90 degrees apart in the same line

  
  

  trans - two identical groups opposite to each other 180 degrees apart

  
• cis-trans isomerism in octahedral complexes-

  monodentate ligands cis-isomer: 2 Chloride ligands are adjacent to each other with their coordinate bonds separated by 90 degrees

  trans-isomer: 2 Chloride ligands are at opposite corners of the octahedral with their coordinate bonds separated by 180 degrees

  
• cis-trans isomerism in octahedral complexes-

  bidentate ligands cis- similar ligands adjacent to eachother

  
  

  trans- on opposite ends

  
• Optical isomerism only occur in _____________ complexes containing 2 or more __________ ligands


  Optical isomerism only occur in octahedral complexes containing 2 or more bidentate ligands
• Which type of cis-trans isomers cannot be shown in optical isomerism and why

  trans-isomers as a mirror image is exactly the same and can be super imposed
• Optical isomerism (revision)


  non-superimposable mirror images about a chiral centre
• optical isomerism in octahedral complexes


  containing two or more bidentate ligands

  non-superimposable images of one another

  
• Cis-platin


  Drug to fight cancer (anti-cancer drug)

  Pt with 2 Cls on left and 2 NH3s on right

  The Pt Binds to N in guanine and adenine changing the DNAs shape so it can't replicate

  
  

  Activation of the cell's own repair mechanism eventually leads to apoptosis (cell death)

  
• Ligand substitution


  A reaction in which one ligand in a complex ion is replaced by another ligand
• Copper (II) sulfate dissolved in water formula


  [Cu(H2O)6]2+
• When


  aqueous ammonia is added drop-wise to[Cu(H2O)6]2+what 2 different reactions are you able to observe (include the colour changes)[Cu(H2O)6]2+ -> Cu(OH)2 -> [Cu(NH3)4(H2O)2]2+

  
  

  pale blue -> pale blue ppt -> dark blue

  
  

  Cu(OH)2 is dissolved in excess ammonia to form [Cu(NH3)4(H2O)2]2+
• What happens when

  excess aqueous ammonia is added to copper(II) sulfate [Cu(H2O)6]2+ (pale blue colour)4 H2O ligands are substituted by 4 NH3 ligands to form[Cu(NH3)4(H2O)2]2+ turning a dark blue colour

  
• What happens when


  excess concentrated hydrochloric acid is added to copper(II) sulfate [Cu(H2O)6]2+ (pale blue colour) 6 H2O ligands are substituted by 4 Cl- ligands to form tetrahedral[CuCl4]2- turning a yellow colour

  
• When


  excess concentrated hydrochloric acid is added drop wise to[Cu(H2O)6]2+ what 2 different reactions are you able to observe (include the colour changes) pale blue -> green -> yellow

  the green still consists of [CuCl4]2- a yellow colour that is mixed with the blue solution(unreacted [Cu(H2O)6]2+). the green is as a result of not all Cu(H2O)6]2+ reacting
• Why is there a change in coordination number when

  concentrated HCl is added to[Cu(H2O)6]2+ (6 -> 4) Chloride ligands are larger in size than water ligands so fewer chloride ligands fit around the central Cu2+ ions
• Colour of chromium (III)

  potassium sulfate dissolved in water ([Cr(H2O)6]3+) Violet
• Colour of chromium (III) sulfate dissolved in water (


  [Cr(H2O)5SO4]+)Green