The isotope of polonium, 218 81 Po , decays by the emission of an -particle with a

The isotope of polonium, ²¹⁸₈₁Po , decays by the emission of an α-particle with a half-life of 183 s.
a. In an accident at a reprocessing plant some of this isotope, in the form of dust, is released into the atmosphere.
Explain why a spillage in the form of a dust is far more dangerous to health than a liquid spillage.
b. It is calculated that 2.4 g of the isotope is released into the atmosphere. The molar mass of polonium is 218 g mol⁻¹. Calculate the initial activity of the released polonium.
c. It is felt that it would safe to re-enter the laboratory when the activity falls to background, about 10 Bq. Calculate how many hours must pass before it is safe to re-enter the laboratory.