Question

An atom has mainly electrons, protons, and neutrons. If the mass of each neutron is reduced to half, and each electron is twice, then the atomic mass of ${}_{12}M{g}^{24}$:

• A. gets twice
  
• B. approximately remain same
• C. approximately get reduced by 5%
• D. approximately get reduced by 25%

Answer 1

The correct option is D approximately get reduced by 25%

The mass of $Mg$ reduces to $25$% when the mass of each neutron is reduced to half. The mass of $Mg$ is 24 (12 protons + 12 neutrons). If the mass of each neutron is halved, the mass of 12 neutrons will become 6, the mass of $Mg$ will become 12 (of protons) + 6 (of neutrons) which in total is 18, which is 75% of the original mass of 24.

$\frac{18}{24}\times 100=75$%

Mass reduced = (100 - 75) % =25 %