All radioactive decompoistion reactions are…………..order reactions.

Answer

**Step-by-Step Solution:**

1. **Understanding Radioactive Decomposition Reactions:**
Radioactive decomposition reactions involve the transformation of unstable nuclei into more stable forms, which results in the emission of radiation. This process is inherently random and occurs at a rate that is characteristic of the particular radioactive isotope.

2. **Defining Reaction Order:**
The order of a reaction refers to the power to which the concentration of a reactant is raised in the rate law. For a reaction to be classified as a first-order reaction, the rate of the reaction must be directly proportional to the concentration of one reactant raised to the first power.

3. **Rate of Radioactive Decay:**
In radioactive decay, the rate of decay (or the rate of the reaction) is proportional to the amount of the radioactive substance present. This means that as the concentration of the radioactive material decreases, the rate of decay also decreases.

4. **Mathematical Representation:**
The mathematical representation of a first-order reaction can be expressed as:
\[ \text{Rate} = k [A]^1 \]
where \( k \) is the rate constant and \([A]\) is the concentration of the radioactive substance.

5. **Conclusion:**
Since the decay rate of a radioactive element is proportional to its concentration raised to the first power, we conclude that all radioactive decomposition reactions are first-order reactions.

**Final Answer:**
All radioactive decomposition reactions are first-order reactions.

---