Which of the following is radioactive alkali metal ?

Options

A. Fr
B. Ra
C. At
D. Rn

Answer

To determine which of the following is a radioactive alkali metal, we can follow these steps:

### Step 1: Identify the Elements
The options given are Francium, Radium, Acetone, and Radon. We need to identify which of these elements are alkali metals.

### Step 2: Classify the Elements
- **Francium (Fr)**: This is an alkali metal and is located in Group 1 of the periodic table.
- **Radium (Ra)**: This is an alkaline earth metal and is located in Group 2 of the periodic table.
- **Acetone**: This is not an element; it is an organic compound (C3H6O).
- **Radon (Rn)**: This is a noble gas and is located in Group 18 of the periodic table.

### Step 3: Determine Radioactivity
Now, we will check which of the identified alkali metals is radioactive.
- **Francium** is known to be radioactive. Its most stable isotope, Francium-223, has a half-life of only about 22 minutes, making it highly radioactive.
- **Radium**, while also radioactive, is not an alkali metal.

### Step 4: Conclusion
Since Francium is the only alkali metal among the options and is also radioactive, we conclude that the answer to the question is **Francium**.

### Final Answer
**Francium** is the radioactive alkali metal.

---