Transition metals

Transition metals - electron configuration, oxidative states, catalytic behaviour, hydroxides........ for OCR Chemistry

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  • Created by: Alice
  • Created on: 11-05-10 18:47

Electron configuration

Definition;

  • A transition element has at least one ion with an incomplete d sub-shell.

Zinc and Scandium are not transition elements as they do not fit the definition. They are known as d-block elements

Zinc - 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10 4s^2 Scandium - 1s^2 2s^2 2p^6 3s^2 3p^6 3d^1 4s^2

Zinc forms an ion that is Zn^2+, this means that the electrons are taken from the 4s^2 subshell leaving Zinc with an unchanged full d-subshell. Transition elements/metals should have an incomplete subshell so zinc is not a transition element but instead a d-block element. Zn^2+ = 1s^2 2s^2 2p^6 3s^2 3p^6 3d^10

Scandium forms an ion that is Sc^3+. It firstly looses the 2 electrons from the 4s^2 subshell followed by the only electron in the 3d^1. Scandium is now left with an electron confinguration with no electrons in the d-subshell, this again doesnt fit the definition of transition element so scandium is not a transtion element but a d-block element. Sc^3+= 1s^2 2s^2 2p^6 3s^2 3p^6

Remember, if a d-block element has a white compound in that oxidative state then it would probably have a full d-subshell or an empty d-subshell.

The transition elements form positive ions as they are metals. This means that when an ion is formed, electrons are removed from the atom. 4s electrons are removed first.

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Oxidative states and catalytic behaviour

Oxidative states - you need to learn these oxidative states.

Iron has common oxidative states of Fe^2+ and Fe^3+

Copper has common oxidative states of Cu+ and Cu^2+

Catalytic Behaviour

Transition elements and their compounds can be very good catalysts for 2 reasons;

  • They have different oxidative states, so they can gain or lose electrons in between oxidative states which facillitates and speeds up the redox reaction
  • They provides sites for reaction to take place as they can bond to a wide range of ions, molecules in solutions and molecules in solids.

Examples of industrial catalysts are:

  • Finely divided Fe in production of ammonia
  • Solid V2O5 in the production of sulfur trioxide, used to make sulfuric acid
  • Finely divided Ni to hydrogenation of alkenes
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Metal hydroxide

Transition metal ions react with hydroxide ions in aqueous solution to give a solid

OH-(aq) + transition metal(aq) > metal hydroxide(s)

Colours of the metal hydroxides can be used to determine the metal.

  • Cu^2+(aq) {blue} + 2OH-(aq) > Cu(OH)2 (s) {blue}
  • Fe^2+(aq) {pale green} + 2OH-(aq) > Fe(OH)2 {green}
  • Fe^3+(aq) {yellow/orange} + 3OH- > Fe(OH)3 {red-brown/ rust}
  • Co^2+(aq) {pink} + 2OH- > Co(OH)2 {blue-green and then pink}
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Comments

purplebrainz

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good notes, thanks, shame the first card is cut off tho

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