Question

What is the oxidation number of a zinc atom with an electronic configuration $\left[ {Ar} \right]3{d^{10}}$?

Answer 1

We need to first understand the concept of oxidation state or oxidation number. The oxidation state, sometimes referred to as oxidation number, describes the degree of oxidation. It defines the loss of electrons of an atom in a chemical compound. Some general rules are to be followed when calculating the oxidation number of any element.

Complete answer:
We have to remember that the rules for finding the oxidation number are discussed as follows:
(i) In a neutral compound, all oxidation numbers must add up to zero. A neutral compound does not have a plus or minus charge.
(ii)In an ion, all the oxidation numbers must add up to the charge of the ion.
(iii) Free elements have an oxidation number of zero(e.g.$Na,Fe,{H_2},{O_2},{S_8}$).
(iv) Another straight-forward rule is Fluorine always has its oxidation number as $- 1$ as it is the most electronegative element and has one electron less to complete its octet.
(v)Elements in the Group 1 of periodic table have an oxidation number of $+ 1$and those of group 2 elements have an oxidation number of $+ 2$.
(vi) Hydrogen when bonded to nonmetals have an oxidation number of $+ 1$ and hydrogen when bonded to metals(or Boron) have an oxidation number of $- 1$.
(vii) Oxygen usually has an oxidation state of $- 2$ with two big exceptions, i.e, when bonded to Fluorine and in peroxides.
(viii)When none of the above rules seem applicable, we can use the group rules. In binary compounds with metals,
• group $17$ elements have oxidation state $- 1$
• group 16 elements have oxidation state $- 2$
• group 15 elements have oxidation state $- 3$
A neutral zinc atom's electron configuration is $\left[ {Ar} \right]3{d^{10}}4{s^2}$.
Since it has lost the two valence electrons $4{s^2}$, a zinc ${2^ + }$ ion has the electron structure $\left[ {Ar} \right]3{d^{10}}$. An ion's oxidation number is the same as its charge (Applying rule ii ).
Hence, the oxidation number of the zinc atom with an electronic configuration $\left[ {Ar} \right]3{d^{10}}$is $+ 2$.

Note:
We must be noted that there are some general rules to be followed when calculating the oxidation number of any element as discussed above. Two important of them are
(i) In a neutral compound, all oxidation numbers must add up to zero. A neutral compound does not have a plus or minus charge.
(ii)In an ion, all the oxidation numbers must add up to the charge of the ion.