Question

Choose the correct statement. The use $^{12}C$ scale has superseded the older scale of atomic mass based on$^{16}O$ isotope, one important advantage of the former being:
A) The atomic masses on $^{12}C$ scale became whole number
B) $^{12}C$ is more abundant in the earth’s crust than $^{16}O$
C) The difference between the physical and chemical atomic masses got narrowed
down significantly.
D) $^{12}C$ is situated midway between metals and non-metals in the periodic table.

Answer 1

The atomic mass refers to the given atoms’ actual physical mass. The atomic mass in the numerical value is very small, that is, why it is measured on the basis of comparison with $^{12}C$ isotope mass. $C - 12$ This is isotopically pure and met the physicists’ need to base the scale on a pure isotope

Complete Step by step answer: Earlier chemists and physicists used two different atomic-mass scales. The chemists used a "atomic mass unit" scale where oxygen isotopes had an atomic mass $16$.while the physicists assigned the same number $16$ to only the atomic mass of the most common oxygen isotope $O - 16$. However, $(O - 17{\text{ }}and{\text{ }}O - 18)$ are also present in natural oxygen this led to two different tables of atomic mass.
The problem was that physics stuck to isotopically pure $O - 16$ for their mass scale, and chemistry used "oxygen"$(O - 17{\text{ }}and{\text{ }}O - 18)$. There's a $0.028\%$ difference between those scales.
The slight variations in the isotopic composition of natural oxygen from different sources. It was considered undesirable to have two different but closely related scales dealing with the same quantities.
They established a new scale, this scale is based on $C - 12$.It is isotopically pure and very close to the previous chemistry scale.

It met the physicists' need to base the scale on a pure isotope, while being numerically close to the chemists' scale. It is get narrow down the difference between physical and chemical atomic masses.$C - 12$, where $1$ Dalton is defined as ​$1 / 12\;$ of the mass of a single $C - 12$ atom, the numeric value of the atomic mass when expressed in daltons has nearly the same value as the mass number.

So the option (C) is correct.

Note: It should be noted that $C - 12$ is the more abundant of the two stable carbon isotopes. It has $98.93\%$ of the element carbon. We can say that Its abundance is due to the triple-alpha process by which it is created in stars.