The value of x in the complex `H_(x) Co(CO)_(4)` is `(Co, Z = 27)`

Options

A. 2
B. 3
C. 1
D. 0

Answer

C

Explanation

We can get the answer by applying the effective atomic number (ENA) rule which says that electron pairs from ligands are needed until the central metal is surrounded by the same number of electrons as the next noble gas. For period 4 elements such as Co, the next noble gasis is `Kr(Z=36)` . Since atomic number of cobalt is 27 and each CO provides 2 electrons, we have
`36 = 27 - (0.N.) + 2xx4`
or `O.N = - 36 + 27 + 2xx4`
`= - 1`
For, `H_(x) Co(CO)_(4)`, the sum of oxidation number must be zero. Thus
`x + (-1) + 4 (0) = )`
`x = 1`