The elements which are radioactive and have been named after the name of planet are

Options

A. `Hg` (Mercury) (Hergentium)
B. `Np` (Neptunium)
C. `Pu` (Plutonium)
D. `Ra`(Radium)

Explanation

To solve the question regarding the elements that are radioactive and named after planets, we can follow these steps:

### Step 1: Identify the elements mentioned in the question.
We need to consider the elements that are radioactive and check if they are named after planets. The elements we will analyze include Mercury, Neptunium, Plutonium, and Radium.

### Step 2: Analyze Mercury.
- **Atomic Number**: 80
- **Radioactivity**: Mercury itself is not a radioactive element, although some of its isotopes are.
- **Planet Name**: Mercury is named after the planet Mercury.

**Conclusion**: Mercury is not a suitable answer since it is not a radioactive element.

### Step 3: Analyze Neptunium.
- **Atomic Number**: 93
- **Radioactivity**: Neptunium is a radioactive element.
- **Planet Name**: Neptunium is named after the planet Neptune.

**Conclusion**: Neptunium is a suitable answer as it is both radioactive and named after a planet.

### Step 4: Analyze Plutonium.
- **Atomic Number**: 94
- **Radioactivity**: Plutonium is a radioactive element.
- **Planet Name**: Plutonium is named after the planet Pluto.

**Conclusion**: Plutonium is also a suitable answer as it is radioactive and named after a planet.

### Step 5: Analyze Radium.
- **Atomic Number**: 88
- **Radioactivity**: Radium is a radioactive element.
- **Planet Name**: Radium is not named after any planet.

**Conclusion**: Radium is not a suitable answer since it is not named after a planet.

### Final Answer:
The elements which are radioactive and have been named after planets are **Neptunium (Np)** and **Plutonium (Pu)**.

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