Uranium hasn't stable isotopes.
All the isotopes of uranium are unstable.Natural isotopes of uranium are: 234, 235 and 238.
The uranium decay chain ends with lead stable isotopes.
The decay chain in the uranium 238 series (also called radium series) id lead 206 (stable isotope).
There is no uranium isotope with 234 neutrons. The questioner almost certainly meant the uranium isotope with 234 nucleons, which is a naturally occurring isotope U234 otherwise element 92, with 142 neutrons.In which case its half life would be 252,000 years.
Uranium 235 is unstable because it is a radioactive isotope. This means that it is constantly decaying and emitting radiation. The reason it is unstable is because it has too many neutrons in its nucleus. The neutron is a unstable particle, and when there are too many of them in one place, they can cause problems. When uranium 235 decays, it emits alpha particles, which are high-energy particles that can damage DNA and cause cancer.
Any isotope of uranium is specific. This notion don't exist.
The final product of the decay chain is the stable isotope 206Pb.
A nuclear reaction between an uranium isotope (e.g. uranium 238) and deuterons.
Uranium-235 is a natural isotope with 143 neutrons. Uranium-231 is an artificial isotope with 139 neutrons.
The atomic number of uranium is 92. The number of neutrons of the isotope uranium-235 is 143.
The end element of the uranium decay chain is a stable isotope of lead.
Uranium-235 is the fissile isotope