Question

Which of the following is the standard for atomic mass?

• A. ${}_8{}^{16}\mathrm{C}$
• B. ${}_6{}^{12}\mathrm{C}$
• C. ${}_1{}^1\mathrm{H}$
• D. ${}_6{}^{14}\mathrm{C}$

Answer 1

The correct option is B

${}_6{}^{12}\mathrm{C}$

The explanation of the correct option:

(B) ${}_6{}^{12}\mathrm{C}$

• An atomic mass unit is considered as either a mass equivalent to one-twelfth the mass of an atom of C-12.
• The C-12 atom contains 6 protons and 6 neutrons including its nucleus.
• ${}_6{}^{12}\mathrm{C}$ is the standard for atomic mass.
• Therefore, the correct option is b.

The explanation of incorrect options:

The other options are incorrect because their mass is not equal to $\frac{1}{{12}^{\mathrm{th}}}$ the mass of an atom. Hence, options (A), (C) and (D) stand incorrect.

Thus, the correct option is (B) ${}_6{}^{12}\mathrm{C}$.