The order of heat of fusion of `T_(2),D_(2) and H_(2)` is

Options

A. `T_(2) gt D_(2) gt H_(2)`
B. `H_(2) gt T_(2) gt D_(2)`
C. `D_(2) gt T_(2) gt H_(2)`
D. `D_(2)=T_(2)gtH_(2)`

Answer

To determine the order of heat of fusion for the isotopes T₂ (tritium), D₂ (deuterium), and H₂ (hydrogen), we need to consider the strength of the bonds formed between the atoms in these molecules. The heat of fusion is the amount of energy required to change a substance from a solid to a liquid at its melting point.

### Step-by-Step Solution:

1. **Identify the Isotopes**:
- H₂ (hydrogen) consists of two hydrogen atoms.
- D₂ (deuterium) consists of two deuterium atoms (which have one neutron in addition to the proton).
- T₂ (tritium) consists of two tritium atoms (which have two neutrons in addition to the proton).

2. **Understand Bond Strength**:
- The bond strength in a molecule is influenced by the mass of the atoms involved. Heavier isotopes generally form stronger bonds due to increased nuclear attraction.
- T₂ has the highest mass, followed by D₂, and then H₂, which is the lightest.

3. **Analyze Heat of Fusion**:
- The heat of fusion is directly related to the strength of the bonds. Stronger bonds require more energy to break.
- Therefore, T₂, with the strongest bonds due to the presence of the heaviest isotope, will have the highest heat of fusion.
- D₂ will have a lower heat of fusion than T₂ but higher than H₂ due to its intermediate mass.
- H₂ will have the lowest heat of fusion because it has the weakest bonds.

4. **Order of Heat of Fusion**:
- Based on the bond strengths, we can conclude the order of heat of fusion is:
- T₂ > D₂ > H₂

### Final Answer:
The order of heat of fusion of T₂, D₂, and H₂ is:
**T₂ > D₂ > H₂**