Heavy water is

Options

A. deuterium oxide
B. tritium oxide
C. rain water
D. water at `4^(@)C`

Explanation

**Step-by-Step Solution:**

1. **Definition of Heavy Water**: Heavy water is chemically known as deuterium oxide (D2O). It is a form of water where the hydrogen atoms are replaced by deuterium, which is an isotope of hydrogen.

2. **Understanding Deuterium**: Deuterium (D) is an isotope of hydrogen that contains one neutron and one proton in its nucleus. This gives deuterium a greater mass compared to the common hydrogen isotope, which has only one proton.

3. **Chemical Composition**: The chemical formula for heavy water is D2O, indicating that it contains two deuterium atoms and one oxygen atom.

4. **Difference from Normal Water**: The primary difference between heavy water (D2O) and normal water (H2O) lies in the hydrogen atoms. In normal water, the hydrogen atoms are protium (the most common hydrogen isotope, which has no neutrons).

5. **Bond Strength**: The bond between deuterium and oxygen in heavy water is stronger than the bond between hydrogen and oxygen in normal water. This is due to the additional neutron in deuterium, which affects the bond characteristics.

6. **Energy Requirement for Separation**: Because of the stronger bonding in D2O, it requires more energy to separate deuterium from oxygen compared to the separation of hydrogen from oxygen in H2O.

7. **Mass Comparison**: Heavy water is termed "heavy" because it has a greater mass than normal water due to the presence of deuterium. This increased mass is a result of the additional neutron in the deuterium atom.

8. **Tritium Oxide**: It's important to note that tritium oxide (T2O) is not commonly found in nature because tritium is radioactive. Therefore, it does not exist in stable forms like deuterium oxide.

9. **Conclusion**: In summary, heavy water (D2O) is defined as deuterium oxide, which is heavier than normal water (H2O) due to the presence of deuterium, and it exhibits stronger bonding characteristics.

**Final Answer**: Heavy water is deuterium oxide (D2O).

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