According to the nuclear reaction `Be_4^x + He_2^4 to C_6^12 +n_0^1`, mass number of (Be) atom is

Options

A. 4
B. 9
C. 7
D. 6

Answer

To determine the mass number of the beryllium atom in the nuclear reaction \( \text{Be}_4^x + \text{He}_2^4 \rightarrow \text{C}_6^{12} + n_0^1 \), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components of the Reaction:**
- The left-hand side (LHS) of the reaction consists of beryllium (Be) and helium (He).
- The right-hand side (RHS) consists of carbon (C) and a neutron (n).

2. **Write Down the Known Values:**
- For beryllium (Be): Atomic number = 4 (denoted as Z), Mass number = x (denoted as A).
- For helium (He): Atomic number = 2, Mass number = 4.
- For carbon (C): Atomic number = 6, Mass number = 12.
- For neutron (n): Atomic number = 0, Mass number = 1.

3. **Set Up the Equation for Mass Numbers:**
- The total mass number on the LHS must equal the total mass number on the RHS.
- LHS: \( x + 4 \) (mass number of Be + mass number of He)
- RHS: \( 12 + 1 \) (mass number of C + mass number of neutron)

4. **Write the Equation:**
\[ x + 4 = 12 + 1 \]

5. **Simplify the Equation:**
\[ x + 4 = 13 \]

6. **Solve for x:**
\[ x = 13 - 4 \]
\[ x = 9 \]

7. **Conclusion:**
- The mass number of the beryllium atom (Be) is 9.

### Final Answer:
The mass number of the beryllium atom is **9**.