In the reaction `Np_(93)^239 to Pu_94^239 + (?)`, the missing particle is

Options

A. Proton
B. Positron
C. Electron
D. Neutron

Answer

To solve the problem, we need to identify the missing particle in the nuclear reaction:

\[ \text{Np}_{93}^{239} \rightarrow \text{Pu}_{94}^{239} + (?) \]

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- The reactant is Neptunium-239 (\( \text{Np}_{93}^{239} \)).
- The product is Plutonium-239 (\( \text{Pu}_{94}^{239} \)).
- We need to find the missing particle represented by (?).

2. **Analyze the Change in Atomic Number**:
- The atomic number of Neptunium (Np) is 93.
- The atomic number of Plutonium (Pu) is 94.
- The atomic number has increased by 1 (from 93 to 94).

3. **Analyze the Change in Mass Number**:
- The mass number of both Neptunium and Plutonium is 239.
- The mass number remains constant (239).

4. **Determine the Type of Decay**:
- Since the mass number is constant and the atomic number increases by 1, this indicates that the reaction is a **beta decay**.
- In beta decay, a neutron in the nucleus is transformed into a proton, and a beta particle (electron) is emitted.

5. **Identify the Missing Particle**:
- In beta decay, the emitted particle is an electron (commonly referred to as a beta particle).
- Therefore, the missing particle in the reaction is an electron.

6. **Write the Complete Reaction**:
- The complete reaction can be written as:
\[ \text{Np}_{93}^{239} \rightarrow \text{Pu}_{94}^{239} + e^- \]

### Final Answer:
The missing particle is an **electron**.

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