Question

Atoms may be regarded as comprising of protons, neutrons and electrons. If the mass attributed to a neutron were halved and that attributed to the electron were doubled, the atomic mass of ${}_6^{12}\text{C}$ would:

• A. remain approximately the same
• B. be approximately doubled
• C. be approximately halved
• D. be reduced approximately by 25%

Answer 1

The correct option is D be reduced approximately by 25%

Mass of a atom $=massofproton+massofneutron$
As mass of electron is very less compare to neutron and proton.
So if mass of neutron is halved then total mass of ${}^{12}\text{C}=6p+\frac{6n}{2}=9$
$\therefore$ % decrease in mass of atom $=\frac{3}{12}\times 100=25$ %