In the following nuclear reaction 'x' stands for `n to p + e^(-) +x`.

Options

A. `alpha-"particle "`
B. positron
C. nutrino
D. antinutrino

Answer

To solve the problem regarding the nuclear reaction where 'x' stands for a particle in the decay of a neutron into a proton and an electron, we can follow these steps:

### Step 1: Understand the Reaction
The reaction given is:
\[ n \rightarrow p + e^- + x \]
Here, \( n \) is a neutron, \( p \) is a proton, and \( e^- \) is an electron (beta particle). We need to determine what 'x' represents.

### Step 2: Analyze Charge Conservation
In nuclear reactions, charge must be conserved.
- The neutron (n) has a charge of 0.
- The proton (p) has a charge of +1.
- The electron (e^-) has a charge of -1.

Calculating the total charge on the right side:
\[ \text{Charge of p} + \text{Charge of e} = +1 + (-1) = 0 \]
Since the left side (neutron) has a charge of 0, the right side must also have a total charge of 0. This means that 'x' must also have a charge of 0.

### Step 3: Identify Possible Candidates for 'x'
The possible candidates for 'x' are:
1. Alpha particle (2 protons + 2 neutrons) - Charge: +2
2. Positron (e^+) - Charge: +1
3. Neutrino (ν) - Charge: 0
4. Antineutrino (ν̅) - Charge: 0

From the candidates, we can eliminate the alpha particle and the positron because they do not have a charge of 0.

### Step 4: Determine the Nature of the Decay
The reaction given is a beta decay, which typically involves the transformation of a neutron into a proton, emitting an electron and an antineutrino.

### Step 5: Conclusion
Since 'x' must be a neutral particle that is emitted during beta decay, the only suitable candidate is the antineutrino (ν̅).

Thus, the answer is:
**x = Antineutrino (ν̅)**

### Final Answer:
**Option D: Antineutrino**

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