Question

Which of the following complexes obeys the EAN rule?

• A. $\left[ Pt \left( NH _{3}\right)_{4}\right]^{2+}$
• B. $\left[ Ni \left( NH _{3}\right)_{6}\right]^{2+}$
• C. $\left[ Cr \left( NH _{3}\right)_{6}\right]^{3+}$
• D. $\left[ Fe ( CN )_{6}\right]^{4-}$

Answer 1

Answer: (D)

$EAN$ rule means that the effective atomic number of the central metal be equal to the atomic number of next noble gas.

For $\left[ Fe ( CN )_{6}\right]^{4-}, Fe$ is in $+2$ oxidation state.

$EAN =26-2+(6 \times 2)=36$

$36$ is equal to the atomic number of the next noble gas $Kr (36)$