The alpha decay of a uranium-238 (\(^{238}\text{U}\)) nucleus can be represented by the following nuclear equation:
\[ ^{238}\text{U} \rightarrow ^{234}\text{Th} + ^{4}\text{He} \]
In this decay process, uranium-238 emits an alpha particle (\(^{4}\text{He}\)) and transforms into thorium-234 (\(^{234}\text{Th}\)).
To break it down:
- The atomic number of uranium-238 is 92 (it has 92 protons).
- When it emits an alpha particle (which has 2 protons and 2 neutrons), its atomic number decreases by 2 (to 90).
- Its mass number decreases by 4 (from 238 to 234).
Therefore, uranium-238 decays to thorium-234 and emits an alpha particle.