The modern basis of expressing atomic and molecular masses is based on

Options

A. O - 16
B. H - 1
C. C - 12
D. Cl - 35.5

Answer

**Step-by-Step Solution:**

1. **Understanding Atomic and Molecular Masses:**
- Atomic mass refers to the mass of a single atom, while molecular mass refers to the mass of a molecule, which is a group of atoms bonded together.

2. **Standard Unit for Atomic Mass:**
- The standard unit used to express atomic and molecular masses is the Atomic Mass Unit (AMU).

3. **Definition of AMU:**
- One Atomic Mass Unit (1 AMU) is defined as one twelfth (1/12) of the mass of a carbon-12 atom.

4. **Carbon-12 as the Basis:**
- The modern basis for expressing atomic and molecular masses is the carbon-12 isotope, which has an atomic mass of exactly 12 AMU.

5. **Why Carbon-12?**
- Carbon-12 is chosen because it is a stable isotope and is abundant in nature. Other isotopes of carbon, like carbon-14, are not used for this purpose.

6. **Conclusion:**
- Therefore, the modern basis of expressing atomic and molecular masses is based on the carbon-12 isotope.

**Final Answer:**
The modern basis of expressing atomic and molecular masses is based on the carbon-12 isotope.

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