Which of the noble gases has its ionisation enthalpy close to that of molecular oxygen?

Options

A. Ar
B. Xe
C. Kr
D. Rn

Answer

To solve the question "Which of the noble gases has its ionization enthalpy close to that of molecular oxygen?", we can follow these steps:

### Step 1: Understand the Concept of Ionization Enthalpy
Ionization enthalpy (or ionization energy) is the amount of energy required to remove an electron from an atom or molecule in its gaseous state. Noble gases are known for their high ionization enthalpies due to their stable electron configurations.

**Hint:** Remember that ionization enthalpy values can be compared to determine similarities between elements.

### Step 2: Gather Ionization Enthalpy Values
We need to find the ionization enthalpy values for molecular oxygen (O2) and the noble gases listed in the options. The first ionization enthalpy of O2 is approximately 1175 kJ/mol.

**Hint:** Look for reliable sources or tables that list the ionization enthalpy values for elements, especially noble gases.

### Step 3: Compare Noble Gases' Ionization Enthalpies
The noble gases listed are:
- Argon (Ar)
- Krypton (Kr)
- Xenon (Xe)
- Radon (Rn)

From known data, the first ionization enthalpy values are approximately:
- Argon: 1520 kJ/mol
- Krypton: 1350 kJ/mol
- Xenon: 1170 kJ/mol
- Radon: 1030 kJ/mol

**Hint:** Identify which noble gas has an ionization enthalpy that is numerically closest to that of molecular oxygen.

### Step 4: Identify the Closest Value
Upon comparing the values, we see that:
- The ionization enthalpy of Xenon (1170 kJ/mol) is very close to that of molecular oxygen (1175 kJ/mol).

**Hint:** Look for the smallest difference between the ionization enthalpy of O2 and the noble gases.

### Step 5: Conclusion
Based on the comparison, we conclude that the noble gas whose ionization enthalpy is closest to that of molecular oxygen is **Xenon**.

**Final Answer:** The correct answer is **Option 2: Xenon**.