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Question: The oxidation number of phosphorus in \({{Ba}}{\left( {{{{H}}_2}{{P}}{{{O}}_2}} \right)_2}\) is: A...

The oxidation number of phosphorus in Ba(H2PO2)2{{Ba}}{\left( {{{{H}}_2}{{P}}{{{O}}_2}} \right)_2} is:
A. +3 + 3
B. +2 + 2
C. +1 + 1
D. 1 - 1

Explanation

Solution

When an atom gains or loses electrons, it attains a charge which is known as oxidation number. It is also known as oxidation state. It can have positive value or negative value or even zero. Since phosphorus is a non-metal, it has oxidation states 3,+5 - 3, + 5 or +3 + 3. But it may vary depending on the atoms attached.

Complete step by step answer:
Let’s calculate the oxidation state of phosphorus in Ba(H2PO2)2{{Ba}}{\left( {{{{H}}_2}{{P}}{{{O}}_2}} \right)_2}.
The given compound can be splitted as Ba2+{{B}}{{{a}}^{2 + }} and (H2PO2)2{\left( {{{{H}}_2}{{P}}{{{O}}_2}} \right)_2}^ - . If the compound has a charge, the sum of oxidation states of each atoms is that charge.
i.e. sum of oxidation states of hydrogen, phosphorus and oxygen is equal to 1 - 1. Let the oxidation state of phosphorus be x{{x}}. We know that the oxidation state of atoms in elementary forms is zero and that of hydrogen is +1 + 1. There are two hydrogen atoms. So the oxidation state will be +2 + 2. Oxidation state of oxygen is 2 - 2.
Now let’s calculate the oxidation state of phosphorus as follows:
(2×+1)+(x×1)+(2×2)=1\left( {2 \times + 1} \right) + \left( {{{x}} \times 1} \right) + \left( {2 \times - 2} \right) = - 1
On simplification we get
(+2)+(x)+(4)=1x2=1x=+1\left( { + 2} \right) + \left( {{x}} \right) + \left( { - 4} \right) = - 1 \Leftrightarrow {{x}} - 2 = - 1 \Leftrightarrow {{x}} = + 1
So we can tell that the oxidation state of phosphorus is +1 + 1.

Hence the correct option is C.

Additional information:
Phosphorus needs a high amount of energy to gain three electrons to attain octet. So it is not the same as that of nitrogen. Nitrogen can form M3{{{M}}^{3 - }} because it has a very high electronegativity and it is very small in size.

Note: Phosphorus is an element which lies in the group 1515. It has five valence electrons. Its bonding behavior influences the oxidation number. Thus we can say that the oxidation number ranges from a value of 3 - 3 to +5 + 5. It is purely dependent on the electronic configuration of phosphorus