Question

In calcium hypophosphite, oxidation number of phosphorus is
(A) 0
(B) +1
(C) +3
(D) +5

Answer 1

To solve this question, we first need to know what the oxidation number is. In a chemical compound, the oxidation number or the oxidation state is used to determine the degree of oxidation of an atom.

Complete answer:
First, let us look at the rules to determine the oxidation number of an element.
- For a free element, the oxidation number of an element in a is always 0.
For example, in helium and nitrogen, the oxidation number of the He and N molecule will be 0.
Similarly, the sum of all the atom's oxidation numbers of a compound that is neutral is 0.
- The oxidation number of an ion, whether it is monatomic or polyatomic, is equal to the charge on the in.
For example, the oxidation number of $M{{g}^{2+}}$ is +2. The oxidation number of phosphate ions $P{{O}_{4}}^{3-}$ is -3.
- The usual oxidation number of
Hydrogen = +1
Oxygen = -2
Group I(A) = +1
Group II(A) = +2
Group VII(A) = -1
Now, let us look at the structural formula of calcium hypophosphite.
$Ca{{({{H}_{2}}P{{O}_{2}})}_{2}}$
From the rules stated above, we can say that
+2 + 2[2(+1) + P + 2(-2)] = 0
P = +1

So, the oxidation number of phosphorus in calcium hypophosphite is option (B) +1.

Note:
-It should be noted that there are some exceptions while assigning the oxidation states of atoms in a molecule.
- When a hydrogen atom is bonded to a less electronegative atom, its oxidation number is -1.
- When an oxygen atom is bonded to a more electronegative atom, it exists in a peroxide ion, its oxidation number changes.
- When a Group VII(A) atom is bonded to a more electronegative atom, its oxidation number changes.