Question

Assertion: Atomicity of oxygen is $2$
Reason: 1 mole of an element contains $6.022 \times {10^{23}}$ atoms.
A) Both assertion and reason are correct and reason is the correct explanation of assertion.
B) Both assertion and reason are correct but reason is not the correct explanation of assertion.
C) Assertion is correct but reason is incorrect.
D) Both assertion and reason are correct.

Answer 1

Hint: As we know that the mole is essentially a count of particles. Usually the particles counted are chemically identical entities, individually distinct. For example, a solution may contain a certain number of dissolved molecules that are more or less independent of each other.

Complete answer:
We need to remember that atomicity is the number of atoms present in a gaseous element. For example in an oxygen molecule, the atomicity is two are two oxygen atoms are present. Atomicity may vary in different allotropes of the same element. There is a simple way to determine the atomicity of any element. It can be determined as a ratio of molecular mass and atomic mass.
We have to remember that one mole of a substance is equal to $6.022 \times {10^{23}}$ units of that substance (such as atoms, molecules, or ions). The number $6.022 \times {10^{23}}$ is known as Avogadro's number or Avogadro's constant.

Thus option B is correct which says both assertion and reason are correct but the reason is not the correct explanation of assertion.

Note:
We have to know that all metals and some other elements, such as carbon, do not have a simple structure but consist of a very large and indefinite number of atoms bonded together. Their atomicity cannot be determined and is usually considered as $1$. Atomicity may vary in different allotropes of the same element. There is a simple way to determine the atomicity of any element. It can be determined as a ratio of molecular mass and atomic mass.