The Oxidation Number of Cobalt in K

The Oxidation Number of Cobalt in[Co(CO)4] is _______.

(a) +1 

(b) +3 

(c) -1 

(d) -3

Ans: (c)

The oxidation number can be defined as the number of electrons available in any compound that is shared with another compound to form a chemical bond. This sharing may include losing or gaining electrons. It is the oxidation number that determines the oxidation state of any chemical compound. 

Moreover, the oxidation number can be described as a charge that appeared over the atom of any chemical compound when they form an ionic bond with any other atom. The atom is considered to have a negative oxidation state if they have a high electronegativity. 

In order to calculate the oxidation number of any compound given in chemical composition, it is necessary, to sum up, the oxidation number of every compound present in that combination and evaluate it with the total oxidation state of that chemical composition to find out the oxidation number of a particular compound.

However, in the given question of finding out the oxidation number of cobalt in K[Co(CO)4], it is necessary to find out the oxidation state of potassium as well as that of carbon monoxide. As the total and the overall oxidation state of the given compound is considered to be zero because it is a neutral or charge less compound. Therefore, the overall expression of finding out the oxidation number of cobalt can be written as;

(Oxidation state of potassium) + (Oxidation state of cobalt) +(Oxidation state of carbon monoxide)

As per the chemical compositions, the oxidation state of potassium is considered to be one and that of carbon monoxide is considered to be zero As well as the overall oxidation state of the given compound is also considered to be zero there for the oxidation state of the cobalt can be substituted as;

1+ (Oxidation state of cobalt)+ (4*0)=0

1+ (Oxidation state of cobalt)+0=0

Oxidation state of cobalt = -1

With the help of the above evaluation, the oxidation number of the Cobalt can be written as -1. Therefore, the correct option is C.