One gram of hydrogen contains 6 ×10²³ atoms. Then 4 grams of He contains

Atomic weight of H is 1 u, therefore 1 g of hydrogen has 1 mole of hydrogen and 1 mole of hydrogen contains $6 \times {10}^{23} \mathrm{atoms}.$

Moles of He present in 4 g of He is:

$$\begin{gathered} \mathrm{Moles}=\frac{\mathrm{Mass}}{\mathrm{Molar} \mathrm{mass}} \\ \mathrm{Moles}=\frac{4 \mathrm{g}}{4 \mathrm{g}/\mathrm{mol}}=1 \mathrm{mole} \end{gathered}$$

Hence, 4 g of Helium also contains $6 \times {10}^{23} \mathrm{atoms}.$