Question

Q 4. The value of atomic masses of all elements is
given by considering Carbon-12 isotope as standard. 1
amu or 1u is specified as 1/12 th the mass of one
atom of carbon-12 isotope. Mass of all elements is
given relative to this standard, hence they are called
relative atomic masses.
Consider three hypothetical elements P, Q and R with
atomic masses X,Y and Z respectively. If the standard
X
Y
X Z
&
Y Y
Y Z
&
X Y
&
Y Y
-&
x" Z
Y
Z​

Answer 1

Answer:

One atomic mass unit is defined as one-twelfth of the mass of one carbon - 12 atom because C-12 is chosen as the standard atom. This is because it has the equal number of protons and neutrons (6) and constitutes most of the matter.

The most abundant isotope of carbon is Carbon - 12.

Thus both Assertion and Reason are correct and Reason is the correct explanation of the Assertion.