Question

If u denotes $1$ atomic mass unit. One atom of an element has mass exactly equal to $Au$, where $A$ is mass number of element.

• A. $A=1$
• B. $A=12$
• C. $A=16$
• D. $A$ can take up any integral value from $1$ to $110$

Answer 1

The correct option is B $A=12$

By definition, Atomic Mass Unit is defined as one twelfth of the mass of an unbound neutral atom of carbon-12 in its nuclear and electronic ground state, and has a value of ${1.66053892110}^{(}27)$ kg.
Hence, $A=12$ for Carbon