Question

Assertion (A) : According to EAN rule, ferricyanide is not a stable complex compound.

Reason (R) : EAN of Fe in ferricyanide is 35.

• A. both A and R are true, R properly explains A
• B. both A and R are true, R does not explain A
• C. A is true, but R is false
• D. A is false, but R is true

Answer 1

The correct option is A both A and R are true, R properly explains A

The 18 electron rule (known as the Effective Atomic Number Rule or EAN rule) was originally proposed by N.V. Sigwick when extending the octet rule proposed by G.N. Lewis in applying it to organometallic compounds. The idea behind both of these rules is that in a compound the sum total of all of the electrons would have the configuration of a noble gas.
EAN = (atomic number - ion charge)
+ (number of ligands * number of electrons per ligands)
and for $\left[Fe\right(CN{)}_6{]}^{-3}$, it is $(26-3)+6\ast 2=35$ so ferricyanide is not a stable complex compound.