AP EAMCET201921 Apr 2019Evening ShiftChemistryCoordination CompoundsActual
Which of the following complex ions is most stable?
Options
- ACo H 2 O 6 3 +
- BCo ( CN ) 6 3 -
- CCo C 2 O 4 3 3 -
- DCoF 6 3 -
Correct answer
B. Co ( CN ) 6 3 -
Step-by-step solution
The stability of a complex ion can be decided with effective atomic number rule. EAN   =   Atomic   number   of   metal - O . N .   of   metal + 2 × C . N . Oxidation number of cobalt in given complex: X - 6   = - 3   X =   + 3 So, EAN   = 27 - 3 + 2 × 6 = 36 . EAN of this complex is equal to the atomic number next noble gas,so it follows EAN rule. So, it is most stable among given complexes.