Question

Radius of hydrogen atom is 0.5 $A^o$. Express its radius in kilometres.

Answer 1

We know that,

$1\stackrel{o}{A}={10}^{-10}m$

and $1m={10}^{-3}km$

$0.5\stackrel{\circ }{A}=0.5\times {10}^{-10}m=5\times {10}^{-11}m=5\times {10}^{-11}\times {10}^{-3}km=5\times {10}^{-14}km$