Given is the representation of the number of molecules of different gases. Which gase(s) is/are placed in the correct position?

Molecular mass of H₂ is 2 g, Mass of He is 4 g, mass of N₂ is 28 g and the mass of CH₄  is 16 g.

• Number of moles in He = given mass/molecular mass
         $\Rightarrow$ $2/4$ $\Rightarrow \mathit{ ½}$
  Number of atoms in 0.5 moles of He = $6.022\times 10\mathit{²³ }\times 0.5$$\Rightarrow 3.011 \times 10\mathit{²³}$

Similarly,

• Number of moles in CH₄ = given mass/molecular mass
        $\Rightarrow$ $4/16$ $\Rightarrow$ $\mathit{¼ }$$\Rightarrow$ $0.25$
  Number of atoms in 0.25 moles of CH₄ =$6.022\times 10\mathit{²³ }\times 0.25$$\Rightarrow$$1.50 \times 10\mathrm{²³}$ 
• Number of moles in H₂ = given mass/molecular mass
   $\Rightarrow$ $1/2$ $\Rightarrow$  $0.5$
  Number of atoms in 0.5 moles of H₂ =$6.022\times 10\mathit{²³ }\times 0.5$$\Rightarrow$$3.011 \times 10\mathrm{²³}$ 
• Number of moles in N₂ = given mass/molecular mass
   $\Rightarrow$ $3/28$ $\Rightarrow$  $0.107$
  Number of atoms in 0.5 moles of N₂ =$6.022\times 10\mathit{²³ }\times 0.107$$\Rightarrow$$0.6452 \times 10\mathrm{²³}$ 

Hence, He & CH₄ are placed in the correct position.