If the diameter of a carbon atom is 0.15 nm, calculate the number of carbon atoms which can be placed side by side in a straight line across length of scale of length 20 cm long.

Diameter of a carbon atom = 0.15 nm= 0.15 X ${{10}^{-9}}$ m

Length along which atoms are to . be placed = 20 cm= 0.2 m

Number of carbon atom which can be placed in the given length =

0.2 / 0 .15 x ${{10}^{-9}}$ = 0.2 x ${{10}^{9}}$ / 0.15 m

= 1.33 x ${{10}^{9}}$ atoms