Which of the following has the highest boiling point?

Options

A. `Ne`
B. `He`
C. `CH_4`
D. `Xe`

Answer

To determine which of the given substances has the highest boiling point, we need to analyze the intermolecular forces and the size of the molecules involved. Here's a step-by-step solution:

### Step 1: Identify the substances
The substances given in the question are:
- Neon (Ne)
- Helium (He)
- Methane (CH₄)
- Xenon (Xe)

### Step 2: Understand the type of intermolecular forces
All the substances listed are non-polar and primarily exhibit Van der Waals forces (also known as London dispersion forces). These forces arise due to temporary dipoles that occur when electron distributions around molecules fluctuate.

### Step 3: Compare the sizes of the molecules
- **Helium (He)**: Smallest atom, very low mass.
- **Neon (Ne)**: Larger than helium but still a noble gas.
- **Methane (CH₄)**: A small molecule, but larger than both helium and neon.
- **Xenon (Xe)**: The largest atom among the options, belonging to the fifth period of the periodic table.

### Step 4: Analyze the effect of size on boiling point
The boiling point generally increases with molecular size due to stronger Van der Waals forces. Larger molecules have a greater surface area, which enhances the strength of these forces.

### Step 5: Determine the boiling points based on size
- **Helium** has the lowest boiling point due to its small size and weak Van der Waals forces.
- **Neon** has a higher boiling point than helium but is still lower than that of methane and xenon.
- **Methane (CH₄)** has a higher boiling point than both helium and neon due to its larger molecular size.
- **Xenon (Xe)**, being the largest and having the strongest Van der Waals forces, will have the highest boiling point among the four.

### Conclusion
Based on the analysis, **Xenon (Xe)** has the highest boiling point among the given options.

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