chemistry

EFFECTIVE ATOMIC NUMBER (EAN)

  

•        The sum of the number of electrons, donated by all ligands and those present on the central metal ion or atom in complex is called as effective atomic number (EAN).

•        Generally EAN of central metal ion will be equal to the number of electrons in the nearest noble gas.

•        If the EAN of the central metal is equal to the number of electrons in the nearest noble gas then the complex possess greater stability.

EAN = [(atomic number of central metal) – (the oxidation state of the metal) + (the number of electrons gained by the metal from the ligands through co-ordination)] = [Z metal – (ox.state of the metal) + 2(coordination number of the metal)].

Ex: 1)	[Fe(CN)6]4–	EAN = [26 – (2) + 2(6)] = 36
2)	[Co(NH3)6]3+	EAN = [27 – 3 + 2(6)] = 36
3)	[Ni(CO)4]	EAN = [28 – 0 + 2(4)] = 36
4)	[Fe(CN)6]3–	EAN = [26 – 3 + 2(6)] = 35
5)	[Ni (CN)4]2–	EAN = [28 – 2+ 2(4)] = 36

6)  [Cu(NH₃)₄]²⁺EAN = [29 – 2 + 4(2)] = 35

7)  [Ag(NH₃)₂]⁺  EAN = [47 – 1 + 2(2)] = 42