Question

In the metal carbonyls of general formula $M(CO{)}_n$ (which follows effective atomic number rule) if M is $Ni$, $Fe$ and $Cr$ then the value of $n$ will be respectively:

• A. 6, 5, 6
• B. 4, 5, 6
• C. 4, 4, 5
• D. 4, 6, 6

Answer 1

The correct option is B 4, 5, 6

$M(CO{)}_n$ follows EAN rule
EAN = Atomic no. of metal - Oxidation state of metal + $2$ coordination number of metal.
$\text{Coordination number}=\frac{EAN-At.No+O.S}{2}$
$\text{Coordination number of}Ni=\frac{36-28+0}{2}=4$
$\text{Coordination number of}Fe=\frac{36-26+0}{2}=5$
$\text{Coordination number of}Cr=\frac{36-24+0}{2}=6$