What is the EAN of cobalt in the complex [Co(NH₃)₆]Cl₃?

36

EAN is effective atomic number and it is represented as:

EAN = Z - (O.N) + 2(C.N) or number of lone pairs donated to central atom

where Z = atomic number

O.N. = oxidation number

C.N. = coordination number

[Co(NH₃)₆]Cl₃ → [Co(NH₃)₆]³⁺ + 3Cl^- 

In [Co(NH₃)₆]³⁺ 

x + 6(0) = +3

x = 3

Co3+ (Z = 27) 

EAN = 27 - 3 + 2(6) = 24 + 12 = 36