In nuclear reaction `"" _(2) He ^(4)+ "" _(z) X ^(A) to "" _(z+2) Y ^(A+3) + R` R denotes

Options

A. electron
B. positron
C. proton
D. Neutron

Answer

To solve the nuclear reaction problem, we need to analyze the given reaction step by step.

### Given Reaction:
\[ \text{He}^{4}_{2} + \text{X}^{A}_{z} \rightarrow \text{Y}^{A+3}_{z+2} + R \]

### Step 1: Conservation of Atomic Number
In nuclear reactions, the total atomic number before the reaction must equal the total atomic number after the reaction.

- Initial atomic number: \(2 + z\) (from He and X)
- Final atomic number: \(z + 2 + \text{atomic number of R}\)

Setting these equal gives us:
\[ 2 + z = z + 2 + \text{atomic number of R} \]

Simplifying this equation:
\[ 2 + z = z + 2 + \text{atomic number of R} \implies \text{atomic number of R} = 0 \]

### Step 2: Conservation of Mass Number
Next, we apply the conservation of mass number. The total mass number before the reaction must equal the total mass number after the reaction.

- Initial mass number: \(4 + A\) (from He and X)
- Final mass number: \(A + 3 + \text{mass number of R}\)

Setting these equal gives us:
\[ 4 + A = A + 3 + \text{mass number of R} \]

Simplifying this equation:
\[ 4 + A = A + 3 + \text{mass number of R} \implies \text{mass number of R} = 1 \]

### Step 3: Identifying R
From the previous steps, we have determined that:
- Atomic number of R = 0
- Mass number of R = 1

This corresponds to a neutron, which has an atomic number of 0 and a mass number of 1.

### Conclusion
Thus, the particle R in the nuclear reaction is a neutron.

### Final Answer:
R denotes a neutron.

---