Thursday 5 April 2012

Transition Metals - the basics

With the written ISA coming up soon after we return, I thought it best to cover Transition Metals first, seeing as this is likely to be the basis of the paper.....

TRANSITION METAL = a metal that can form one or more stable ions with a partially filled d-subshell

- A d-subshell can fit 10 electrons in, so transition metals must form an ion that has between 1 and 9 electrons in this subshell
- It is this incomplete d-subshell that creates the key characteristics that define a transition metal
---> Scandium only forms one ion Sc3+, which has an empty d-subshell. Electron configuration for Sc is[Ar]3d14s2 so for Sc3+it is just [Ar].
---> Zinc also only forms one ion, Zn2+, which has a full d-subshell. Electron configuration for Zn is
[Ar]3d104s2so for Zn2+is just [Ar]3d10.
Transition Metals have four important characteristics in common:
1. Complex Formation
---> complex ion is formed when a transition metal is surrounded by ions or other molecules
2. Formation of Coloured Ions
---> majority of metal ions are coloured
3. Variable Oxidation States
---> have more than one oxidation state in their compounds and therefore take place in many redox reactions
4. Catalytic Activity
---> affect the rate of reaction without being used up or chemically changed themselves
LIGAND = an ion or molecule with a lone pair of electrons that can form a dative covalent bond
COMPLEX = central metal ion surrounded by ligands (2, 4 or 6)
CO-ORDINATION NUMBER = the number of dative covalent bonds formed
Unidentate = 1 dative covalent bond            e.g [Cu(CN)6]4-          [Co(OH)2(H20)2]
      
Bidentate = 2 dative covalent bonds            e.g [Co(en)3]2+         [Cr(C2O4)]3-
Hexadentate = 6 dative covalent bonds        e.g [Cu(edta)]1-



    

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