Read the passage given below and answer the following questions:
In spite of the predictions of stable noble gas compounds since at least 1902, unsuccessful attempts at their synthesis gave rise to the widely held opinion that noble gases are not only noble but also inert. It was not until 1962 that this dogma was shattered when Bartlett in Canada published the first stable noble gas compound `XePtF_(6)` . This discovery triggered a worldwide frenzy in this area, and within a short time span many new xenon, radon, and krypton compounds were prepared and characterized. The recent discoveries show the ability of xenon to act as a ligand . The discovery by Seppelt’s group that more than one xenon atom can attach itself to a metal center which in the case of gold leads to surprisingly stable Au- Xe bonds. The bonding in `[AuXe_(4)]^(2+)` involves 4 Xe ligands attached by relatively strong bonds to a single Au(II) center in a square planar arrangement with a Xe-Au bond length of about 274 pm This discovery provides not only the first example of multiple xenon ligands but also represents the first strong metal - xenon bond.
(Source: Christe, K. O. (2001). A renaissance in noble gas chemistry. Angewandte Chemie International Edition, 40(8), 1419-1421.)
Compounds of noble gases except _______ are known.

Options

A. Krypton
B. Radon
C. Helium
D. Xenon

Answer

To solve the question regarding the noble gas compounds, we will analyze the information provided in the passage step by step.

### Step-by-Step Solution

1. **Identify the Noble Gases**: The noble gases include Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), and Radon (Rn).

2. **Review the Passage**: The passage discusses the discovery of stable compounds formed by noble gases, particularly focusing on xenon, radon, and krypton. It mentions the first stable noble gas compound `XePtF_(6)` and highlights the ability of xenon to act as a ligand.

3. **Determine Known Compounds**: According to the passage:
- Compounds of xenon, radon, and krypton are known.
- Specific examples include:
- Xenon: `XeF_(6)`, `XePtF_(6)`, `XeF_(4)`, `XeO_(3)`
- Krypton: `KrF_(2)`
- Radon: `RnF_(2)`

4. **Identify the Exception**: The question asks which noble gas does not have known compounds. The passage does not mention any stable compounds for Helium, suggesting that it is the exception.

5. **Conclusion**: Based on the information analyzed, the compounds of noble gases except Helium are known.

### Final Answer
Compounds of noble gases except **Helium** are known.