Question

Which of the following statements is not true about atomic mass?

• A. The atomic mass of an element is expressed relative to ${ }^{12} C$ isotope of carbon
• B. Atomic mass of $Na$ is $23$ .
• C. The atomic mass of an atom is obtained by taking sum of atomic masses of different isotopes of the element.
• D. Atomic mass used for an element is the average atomic mass obtained by taking into account the natural abundance of different isotopes of that element.

Answer 1

Answer: (C)

Atomic mass is a weighted average of all the isotopes of that element, in which the mass of each isotope is multiplied by the abundance of that particular isotope. It is also expressed relative to $C^{12}$ isotope of carbon, also atomic mass of $N a$ is $23$ .