Answer
92U^235→90Th^231+2He^4
Explanation
Uranium-235 produces thorium-231 by alpha decay.
An α-particle is a helium nucleus. It contains 2 protons and 2 neutrons, for a mass number of 4.
During α-decay, an atomic nucleus emits an alpha particle. It transforms (or decays) into an atom with an atomic number 2 less and a mass number 4 less.
Thus, uranium-238 decays through α-particle emission to form thorium-231
92U^235 → 90Th^231 + 2He^4
If all you are getting is Th then the balanced equation is written below
[tex]_{92}^{235}\text{U} \longrightarrow _{90}^{231}\text{Th +}_{2}^{4}\text{He}[/tex]
The Uranium 235 decays into Thorium 231 and an alpha particle.
I'm not sure this decay happens in nature, but Uranium 238 does decay this way.
