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chimanshu_007

This is an imp. rule...it explains the stability of complexes on the basis on effective atomic number -:

EAN of a metal in a complex is the no. of electrons present in the metal ion plus the no. of electrons donated to it by the ligands.

this may be calculated as

EAN of metal in a complex = At. No - Oxdn state + 2 x co-ordination no.

A stable complex is formed , if the EAN is = to the atomic ni. of next noble gas

for example....

[Co(NH3)6]³⁺.....oxdn state = + 3 .....at no. = 27....co-ord. no = 6......

so its EAN = 27 - 3 + (2x6) = 36 i.e at no. of Kr

This rule can also be used to calculate the no. of ligands attatched to a meta ion/atom.....

eg..

a) To calculate the no. of CO that can b attatched to Ni

at no. of Ni = 28

At no. of next noble gas = 36

no. of electrons to b provided by the ligands = 36-28 = 8

as each CO provides 2 electrons , no. of CO grps to be attatched to Ni = 8/2 = 4

so it is [Ni(co) ₄ ]

or take eg of Fe

at. no. of Fe = 26

next noble gas config. = 36

so no. of electrons = 10

so 5 CO molecules

i.e [Fe(CO)₅)

HOPE THAT IT HELPS U ALLL

ALL THE BEST...

CHEERS! ! ! !! !