Calculate the number atoms in $0.2$ mole of sodium $\left(\mathrm{Na}\right)$.

We are aware that every chemical has an Avogadro number of atoms in one mole.
A chemical has an Avogadro number of atoms per mole.
NA is the symbol used to represent an Avogadro number.
The Avogadro number is equal to $6.02\times {10}^{23}$ atoms.

The answer to the question is that we must determine how many atoms make up 0.2 moles of sodium.
The chemical symbol for sodium is Na, and it is a member of the s-block.
One mole of sodium is known to contain an Avogadro number of atoms.

One mole of a chemical = Avogadro number of atoms. The value of Avogadro number is $6.02\times {10}^{23}$.

One mole of sodium contains Avogadro number of atoms. Hence $0.2$ mole of sodium has:

$0.2\times 6.02\times {10}^{23}$ atoms i.e. $1.2046\times {10}^{23}$.

Hence option (B) is correct.