Question

Atoms may be regarded as comprising of protons, neutrons and electrons. If the mass attributed by electrons was doubled and that attributed by neutrons was halved, the atomic mass of ${}^{12}C$ would be :

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

Answer 1

The correct option is C reduced approximately 25%

Reduced approximately by 25% is the correct option.The mass of electron is negligible.
Atomic mass = mass of protons + mass of neutrons = 6 + 6 =12.
If the mass of neutons is halved, then atomic mass = 6+3=9.
Now 9 is approximately 25% of 12. Hence, the correct option is (c)