Which factor is most responsible for the increase in boiling points of noble gases from He to Xe?

Options

A. decrease in I.E.
B. monoatomic nature
C. decrease in polarisability
D. increase in polarisability

Explanation

To determine which factor is most responsible for the increase in boiling points of noble gases from helium (He) to xenon (Xe), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Noble Gases**: The noble gases in question are helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

2. **Observe the Trend in Boiling Points**: As we move down the group from He to Xe, we notice that the boiling points of these gases increase significantly.

3. **Understand the Concept of Polarizability**: Polarizability refers to the ability of an electron cloud around an atom to be distorted by an external electric field or by the presence of nearby particles. Larger atoms with more electrons generally have higher polarizability.

4. **Relate Size to Polarizability**: As we move down the group from He to Xe, the atomic size increases due to the addition of electron shells. This increase in size leads to an increase in polarizability.

5. **Connect Polarizability to Van der Waals Forces**: The increase in polarizability results in stronger Van der Waals forces (dispersion forces) between the atoms. These forces arise due to temporary dipoles that occur when electron distributions around atoms fluctuate.

6. **Explain the Effect on Boiling Points**: Stronger Van der Waals forces mean that more energy is required to separate the atoms when transitioning from the liquid to the gaseous state. Therefore, as the strength of these forces increases with polarizability, the boiling points of the noble gases also increase.

7. **Conclusion**: The most responsible factor for the increase in boiling points of noble gases from He to Xe is the increase in polarizability due to the increase in atomic size.

### Final Answer:
The factor most responsible for the increase in boiling points of noble gases from He to Xe is the increase in polarizability.

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