Fill in the blank

Answer

To solve the problem, we need to analyze the given nuclear reaction and apply the principles of conservation of mass number and atomic number.

### Step-by-Step Solution:

1. **Identify the Given Reaction**:
The reaction provided is:
\[ \text{N}_{14}^{7} + \text{He}_{4}^{2} \rightarrow \text{H}_{1}^{1} + \text{X} \]
Here, \(\text{N}_{14}^{7}\) represents nitrogen with a mass number of 14 and an atomic number of 7, and \(\text{He}_{4}^{2}\) represents the helium nucleus (alpha particle) with a mass number of 4 and an atomic number of 2.

2. **Write Down the Conservation Laws**:
- **Conservation of Mass Number**: The total mass number before the reaction must equal the total mass number after the reaction.
- **Conservation of Atomic Number**: The total atomic number before the reaction must equal the total atomic number after the reaction.

3. **Calculate the Total Mass Number Before the Reaction**:
\[ \text{Mass number before} = 14 + 4 = 18 \]

4. **Calculate the Total Atomic Number Before the Reaction**:
\[ \text{Atomic number before} = 7 + 2 = 9 \]

5. **Set Up the Equations for the Products**:
Let the mass number of species X be \(A\) and its atomic number be \(Z\). The products of the reaction are hydrogen (\(\text{H}_{1}^{1}\)) and species X.

- The mass number equation:
\[ 1 + A = 18 \quad \Rightarrow \quad A = 18 - 1 = 17 \]

- The atomic number equation:
\[ 1 + Z = 9 \quad \Rightarrow \quad Z = 9 - 1 = 8 \]

6. **Identify Species X**:
Now that we have \(A = 17\) and \(Z = 8\), we can identify species X. The element with atomic number 8 is oxygen (O). Therefore, species X is \(\text{O}_{17}^{8}\).

### Final Answer:
The species X formed in the reaction is \(\text{O}_{17}^{8}\).