Chemistry > Coordination Compounds > 7.0 Effective atomic number
Coordination Compounds
1.0 Basics
2.0 Addition Salt
3.0 Nomenclature of Co-ordination Compounds
4.0 Werner's Co-ordination Theory
5.0 Valence bond theory
6.0 Crystal field splitting theory (CFST)
7.0 Effective atomic number
8.0 Magnetic Moment
9.0 Application of Crystal Field Splitting Theory (CFST)
10.0 Isomerism in Co-ordination compounds
11.0 Organo-metallic compounds
12.0 Stability of Co-ordination compounds
7.1 How to find oxidation number
Oxidation of central metal atom can be calculated from the charge on the complex ion by assuming it be $X$. The sum of the oxidation number of all the species other than that of central metal ion and $X$ (the assumed value of the oxidation of central metal atom ) is put equal to charge of the complex ion, then value of $X$ can be calculated.
Example: ${K_4}\left[ {Fe{{(CN)}_6}} \right]$
Let us assume the oxidation number of $Fe$ be $x$.
$$= 4\times(+1) +\ x\ + 6\times(-1) =0$$$$\therefore x = 6 -4 = +2$$
The oxidation number of $Fe =$ $+2$
Example: ${\left[ {CoCl{{(N{H_3})}_5}} \right]^{ + 2}}$
Let us assume the oxidation number of $Co$ be $x$.
$$x - 1 +5\times(0) = +2$$$$x = +3$$
The oxidation number of $Co$ $= +3$
(we have to take whatever the charge present on the complex so, we have to equal to that charge number like above example)
| S.No. | Atomic number | Complex | Electron lost in ion formation | Electron gain Co-ordination compound | E.A.N | Atomic number of next inert gas |
| 1. | $Fe$ | ${\left[ {Fe(C{N_6})} \right]^{ + 2}}$ | $2$ | $2 X 6 =12$ | $26-2+12=36$ | $36(Kr)$ |
| 2. | $Fe$ | ${\left[ {Fe(C{N_6})} \right]^{3 - }}$ | $ 3$ | $2 X 6 =12$ | $26-3+12=35$ | $36(Kr)$ |
| 3. | $Co$ | ${\left[ {Co{{(N{H_3})}_6}} \right]^{3 + }}$ | $3$ | $2 X 6 =12$ | $27-3+12=36$ | $36(Kr)$ |
| 4. | $Ni$ | $\left[ {Ni{{(CO)}_4}} \right]$ | $0$ | $2 X 4 =8$ | $28-0+8=36$ | $36(Kr)$ |
| 5. | $Cu$ | ${\left[ {Cu{{(CN)}_4}} \right]^{3 - }}$ | $1$ | $2 X 4 =8$ | $29-1+8=36$ | $36(Kr)$ |
| 6. | $Cr$ | ${\left[ {Cr(N{H_3})} \right]^{3 + }}$ | $ 3$ | $2 X 6 =12$ | $24-3+12=33$ | $36(Kr)$ |
