Select the incorrect order .

Options

A. `He gt Ar gt Kr gt Ne gt Xe`-(abundance in air).
B. `He lt Ne lt Ar lt Kr lt Xe`-(boiling point).
C. `XeF_(6) gt XeF_(4) gt XeF_(2)`- (melting point)
D. `XeF_(6) lt XeF_(4) lt XeF_(2)-` (Xe-F bond length)

Answer

To solve the question of selecting the incorrect order from the given options, we will analyze each order provided in the question step by step.

### Step 1: Analyze the Order of Noble Gases in Air
- The first order given is related to the abundance of noble gases in the air. The correct order based on abundance is:
1. Argon (Ar)
2. Neon (Ne)
3. Krypton (Kr)
4. Helium (He)
5. Xenon (Xe)

- If the order provided in the question does not match this correct order, then it is incorrect.

### Step 2: Check the Boiling Point Order
- The second order relates to the boiling points of noble gases. The general trend is that as we move down the group from Helium to Xenon, the boiling point increases due to the increase in atomic size and van der Waals forces.

- The correct order of boiling points from lowest to highest should be:
1. Helium (He)
2. Neon (Ne)
3. Argon (Ar)
4. Krypton (Kr)
5. Xenon (Xe)

- If the order provided matches this trend, it is correct.

### Step 3: Check the Melting Point Order
- The third order given is about the melting points of xenon compounds, particularly with chlorine and fluorine. As the number of chlorine or fluorine atoms increases, steric hindrance increases, and bond length decreases, leading to stronger bonds and higher melting points.

- The expected trend is that more fluorine leads to higher melting points due to stronger bonds. If the order given matches this trend, it is correct.

### Step 4: Check the Bond Length Order
- The fourth order is related to bond lengths in xenon compounds. As the number of fluorine atoms increases, the bond length decreases.

- The expected order from longest bond length to shortest should be:
1. XeF2 (least number of fluorine)
2. XeF4
3. XeF6 (most number of fluorine)

- If the order given matches this trend, it is correct.

### Conclusion
After analyzing all the provided orders:
- The first order regarding the abundance of noble gases in air is found to be incorrect.
- Therefore, the answer to the question is **A** (the order of noble gases based on abundance in air).