Final answer:
Protactinium-234 is considered more dangerous than uranium-234 due to its shorter half-life and the higher penetrating ability of the beta particles it emits compared to the alpha particles from uranium-234.
Step-by-step explanation:
If you were sitting near a gram of protactinium-234 and a gram of uranium-234, both solid materials, which would you consider more dangerous to you? The correct answer is A) Protactinium-234. The danger from radioactive substances is primarily due to two factors: the half-life of the isotope and the type of radiation it emits.
Firstly, with a half-life of 24,000 years, protactinium-234 is more radioactive and thus decays at a faster rate compared to uranium-234, which has a half-life of 246,000 years. This means protactinium-234 would deliver a higher dose of radiation over the same period.
Secondly, the type of radiation emitted also plays a role. Protactinium-234 primarily emits beta particles, whereas uranium-234 emits alpha particles. Although alpha particles are highly ionizing and damaging to biological tissue, they have low penetration and can be stopped by the skin or a sheet of paper. Beta particles, on the other hand, have higher penetration and can reach internal organs more easily, posing a greater risk if the source is external. Considering these points, protactinium-234 would pose a more immediate external radiation danger compared to uranium-234.