Question

The element in the missing box is _______.
238/92 U - 4/2 He + 234/90 _____

Answer 1

To determine the missing element in the nuclear reaction, we need to balance the atomic numbers and mass numbers on both sides of the equation.

We have:

- **Left side**:
- Uranium (U): \(238/92\)
- Helium (He): \(4/2\)

- **Right side**:
- Uranium (He): \(234/90\)
- Missing element: \(X\)

**Balancing the mass numbers (top numbers)**:
\[
238 = 4 + 234 + \text{mass number of } X
\]
\[
238 = 238 + \text{mass number of } X
\]
This gives us:
\[
\text{mass number of } X = 238 - 238 = 0
\]

**Balancing the atomic numbers (bottom numbers)**:
\[
92 = 2 + 90 + \text{atomic number of } X
\]
\[
92 = 92 + \text{atomic number of } X
\]
This gives us:
\[
\text{atomic number of } X = 92 - 92 = 0
\]

An element with atomic number 0 and mass number 0 is a neutron. However, since we are looking for a specific element and commonly refer to nuclear particles, for this reaction, the missing particle corresponds to **the nucleus after alpha decay**, which typically results in a **Thorium (Th) nucleus.**

Thus, the final answer for the element in the missing box is:
**Th (thorium)**.

So, the complete equation is:
\[
238/92 U \rightarrow 4/2 He + 234/90 Th
\]