Q2. Assertion (A): One atomic mass unit is defined as one-twelfth of the mass of one carbon-12 atom. Reason (R): Carbon-12 isotope is the most abundant isotope of carbon and has been chosen as the standard. (i) Both A and R are true and R is the correct explanation of A. (ii) Both A and R are true but R is not the correct explanation of A. (iii) A is true but R is false. (iv) Both A and R are false.
Answer. Correct Option is (i) Both A and R are true and R is the correct explanation of A. Since C-12 is used as the standard atom, one atomic mass unit is defined as one-twelfth of the mass of one carbon – 12 atom. This is due to the fact that it has an equal number of protons and neutrons (6) and makes up the majority of matter. Carbon-12 is the most abundant isotope of carbon.
