[tex]1\ nm = 10^{-9} m\\\\1\ m =\frac{1\ nm}{10^{-9}}[/tex]
Since the diameter of helium atom is approximately [tex]9.8\times 10^{-11}\ m[/tex], therefore the diameter of helium atom in nano meter,
[tex]9.8\times 10^{-11}\ m=9.8\times 10^{-11} \times\frac{1\ nm}{10^{-9}}=0.098\ nm[/tex]
