Each element has a characteristic atomic mass. The atoms are extremely small particles and it is very difficult to determine their actual masses. For example, mass of one atom of hydrogen has been found to be `1.66 xx 10^(-24)` . Obviously, such a small mass cannot be determined even with the help of a very sensitive balance. To overcome, this problem, the atomic masses are expressed as relative masses i.e., with reference to mass of a standard atom. In 1961, the International Union of Chemists selected the stable isotope of carbon ( carbon -12) as the standard for comparing the atomic and molecular masses of elements and compounds. The atomic mass of the standard, the isotope carbon-12 of carbon is chosen to be 12. Thus, atomic mass may be defined as the relative mass of an atom of the element as compared to an atom of carbon ( carbon-12) taken as 12.
Which of the following represents 1 amu ?

Options

A. Mass of C-12 atom
B. Mass of O-16 atom
C. `1//12^(th)` of mass of C-12 atom
D. Mass of hydrogen molecule

Explanation

To determine which of the following represents 1 atomic mass unit (amu), we need to understand the definition of an atomic mass unit.

### Step-by-Step Solution:

1. **Understanding Atomic Mass Unit (amu)**:
- An atomic mass unit (amu) is defined as one twelfth (1/12) of the mass of a carbon-12 atom.

2. **Mass of Carbon-12**:
- The mass of a carbon-12 atom is taken as 12 amu. Therefore, to find 1 amu, we can express it mathematically:
\[ 1 \text{ amu} = \frac{1}{12} \times \text{mass of carbon-12 atom} \]

3. **Calculating 1 amu**:
- Since the mass of a carbon-12 atom is defined as 12 amu, we can conclude:
\[ 1 \text{ amu} = \frac{12 \text{ amu}}{12} = 1 \text{ amu} \]
- Thus, 1 amu is essentially the mass of 1/12 of a carbon-12 atom.

4. **Conclusion**:
- Therefore, the correct representation of 1 amu is the mass of one atom of carbon-12 divided by 12.

### Answer:
1 amu is represented as \( \frac{1}{12} \) of the mass of a carbon-12 atom.

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