Calculate the mass of an $\displaystyle \alpha$-particle in atomic mass unit ( u ). Given, Mass of a normal helium atom $\displaystyle =4 \cdot 002603 \mathrm{u}$ Mass of carbon atom $\displaystyle =1.9926 \times 10^{-26} \mathrm{~kg}$

$\displaystyle 1 \mathrm{u}=\frac{1}{12}$ mass of carbon atom $\displaystyle =\frac{1.9926 \times 10^{-26} \mathrm{~kg}}{12}=1.66 \times 10^{-27} \mathrm{~kg}$ mass of an electron $\displaystyle =9.1 \times 10^{-31} \mathrm{~kg}$ mass of two electrons $\displaystyle =\frac{2 \times 9.1 \times 10^{-31}}{1.66 \times 10^{-27}}=0.00109638 \mathrm{u}$ mass of $\displaystyle \alpha$-particle $\displaystyle =$ mass of the normal helium atom $\displaystyle -$ mass of two electrons $\displaystyle =4.0026030-0.00109638$ $\displaystyle =4.00150662 \mathrm{u}$