Question

Ratio mass of an electron to that of the mass of hydrogen atom is?
(ans= 1:1837)

Answer 1

Mass of the electron is calculated from the charge and e/m value.
$$\begin{gathered} Massofelectron=\frac{Charge}{Charge/mass}=\frac{e}{e/m}=m \\ =\frac{1.602\times {10}^{-19}}{1.759\times {10}^{11}}=9.1\times {10}^{-31} \\ Massofonegramatomofhydrogen=1.008g \\ Massofonehydrogenatom=\frac{1.008}{6.023\times {10}^{23}}=1.673\times {10}^{-24} \\ Whenwecomparethemassofanelectronandmassofhydrogen, \\ \frac{Massofelectron}{Massofonehydrogenatom}=\frac{9.1\times {10}^{-31}}{1.673\times {10}^{-27}}=\frac{1}{1837} \\ Thusthemassofanelectronis1/1837timesthatofhydrogenatomi.e.,mass \\ ofanelectronismuchsmallerthanmassof1hydrogenatom. \end{gathered}$$