Question

The difference between valency and oxidation number are following except:
A. Valency of an element is a fixed quantity whereas oxidation number varies from compound to compound.
B. Valency is a pure number whereas oxidation number has positive or negative value.
C. Oxidation number and valency are having fixed value.
D. Valency and oxidation number can be represented for an element or a radical.

Answer 1

Hint: We should be having a clear concept regarding the definition of oxidation and valency. Moreover their trends along the periodic table should also be known to us.

Step by step answer:
Among the given options, Option A stands true because valency depends on the atomic number of the element. And so it is fixed. And the oxidation number is varied in the compounds depending on the participation in the chemical reaction. So Option A is not the answer.

Next moving on to Option B. Valency is a pure number, because it depends on the number of electrons that the element can lose or gain to attain octet configuration. And the oxidation number can be positive if the element loses an electron for the formation of the compound. And negative, if the element gains an electron for the formation of the compound. So Option B is not the answer.

Option C is incorrect because the value of valency is not fixed and varies along with the period and the oxidation number is also not fixed and varies from compound to compound. So, Option C is not correct.

Option D stands true because valency and oxidation number can be of both, an element as well as for a radical.

So, as we can see, the only exception is the difference between valency and oxidation number is Option C. So, the correct answer is Option C.

Note: Valency across a group in the periodic table, first increases and then decreases. The valency does not change across the group because the bonding behaviour is not affected by the core of electrons.