Question

The present atomic weight scale is based on:
A) ${C^{12}}$
B) ${O^{16}}$
C) ${H^1}$
D) ${C^{13}}$

Answer 1

Hint: We know that ${C^{12}}$ and ${C^{13}}$ are the two isotopes. Each of them has an equal number of protons and electrons, thus the same atomic number. The atomic number of isotopes is six. But carbon-$12$ has six neutrons while carbon-$13$ has $7$ neutrons. Hence, to characterize present day nuclear weight scale should indicate carbon iota addresses the scale.

Complete answer:
Usually, the atomic weight of an atom is equal to the number of protons or electrons in an atom. Hence, lots of elements have isotopes and they use average atomic mass. On the periodic table, the weight of carbon is noted as $12.01\,amu$ which is the average mass of the carbon atom.
Current nuclear weight scale depends on ${C^{12}}$. The standard unit for communicating the mass of iota is amu (nuclear mass unit). It is equivalent to \[\frac{1}{{12}}\] of the mass of a particle of carbon-$12$ . Hence option A is correct.

Additional information:
Researchers settled on utilizing the carbon-$12$ nuclide as the reference standard by which any remaining masses would be analyzed. By definition, one molecule of carbon-$12$ is appointed a mass of $12$ nuclear mass units (amu). A nuclear mass unit is characterized as a mass equivalent to one twelfth the mass of a particle of carbon-$12$ . The mass of any isotope of any component is communicated according to the carbon-$12$ norm. For instance, one iota of helium-$4$ has a mass of \[4.0026\] amu. An iota of sulfur-$32$ has a mass of \[31.972\] amu.

Note:
We have to know that the masses of individual iotas are extremely small. Utilizing a cutting edge gadget called a mass spectrometer; it is feasible to gauge such microscopic masses. A particle of oxygen-16, for instance, has a mass of \[2.66 \times {10^{ - 23}}g\]. While correlations of masses estimated in grams would have some value, it is undeniably more pragmatic to have a framework that will permit us to all more effectively think about relative nuclear masses.