Question

The mass of $\alpha$-particle is

• A. less than the sum of masses of two protons and two neutrons
• B. equal to mass of four protons
• C. equal to mass of four neutrons
• D. equal to sum of masses of two protons and two neutrons

Answer 1

Answer: (A)

$\alpha$-particle $={ }_{2} He ^{4}$. It contains $2 p$ and $2 n$.
As some mass is converted into binding energy, therefore, mass of $\alpha$ particle is slightly less than sum of the masses of $2 p$ and $2 n$.