Question

Which of the following statements does not explain the difference between valency and oxidation number?
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 have fixed values.
D. Valency and oxidation number can be represented for an element or a radical.

Answer 1

The capacity of an atom to combine with other atoms to form a molecule is known as its valency. The number of bonds that an atom forms with other atoms is going to depend on the valency of the particular atom.
Whereas, oxidation number is the charge present on the atom or molecule.

Complete step by step answer:
- Coming to given options, option A, Valency of an element is a fixed quantity whereas oxidation number varies from compound to compound. Option A is correct because valency is related to atomic number of the element it does not change. But the oxidation number of an element is going to vary from one compound to another and depends on the chemical reaction in which it participates.
- Coming to option B, Valency is a pure number whereas oxidation number has positive or negative value. Option B is also correct. Because the valency of an atom is nothing but the number of valence electrons present it is a pure number that has no sign. The oxidation number will be positive or negative depending on the losing or gaining of electrons.
- Coming to option C, Oxidation number and valency have fixed values. Option C is incorrect. Because valency is not fixed and changes along with the period and oxidation number also not fixed and it changes from compound to compound.
- Coming to option D, Valency and oxidation number can be represented for an element or a radical. It is true because we can represent valency and oxidation number for an element and for a radical.
- Therefore, option C is the only exceptional case related to valency and oxidation number.

- So, the correct option is C.

Note: Valency of the atoms first increases and then decreases as we are moving from left to right in the periodic table. But the valency of the atom is not going to change along the groups from top to bottom in the periodic table.