What is the effective atomic number of dichlorobis(ethylenediamine)cobalt(III)?
1 Answer
36 .
The effective atomic number is an old term meaning the sum of ALL the electrons for the central atom and the donated valence electrons from the surrounding ligands, using the appropriate electron-counting scheme.
We will use something I call the "oxidation state" counting scheme, wherein each single-oxidation-state atom is taken as its common oxidation state, and the sum of the charges adds up to the charge of the complex.
[Co(en)2Cl2]+
has oxidation states as
[+3Co 2(0)(en)2 2(−1)Cl2]+ ,since we take
en , ethylenediamine, to be a neutralσ donor, and eachCl ligand to be theCl− π donor.
- Thus,
2(−1)+[?]=+1 , and[?]=+3 for cobalt cation, which means a total of27−3=24 electrons forCo3+ . Cl− in compounds donates two valence electrons as:Cl− .en ,
a bidentate ligand, donates two electrons from each (of two) nitrogen heads as
H2∣N: , for a total of four valence electrons per ligand.
Indeed,
That gives
