All the disintegrations of a sample of an unknown nuclide weighing 4.6 × 10^-²g were counted. In the first half-life of the sample, the total number of disintegrations counted was 4.3 × 10²⁰. What is the atomic weight of the unknown element?

Question

Quizplus · Accepted Answer

The number of disintegrations in the first half-life is equal to the initial number of atoms, which is 4.3 × 10^20. The mass of the sample is 4.6 × 10^-2 g. The atomic weight (A) can be calculated using the formula: A = (mass of sample / number of atoms) × Avogadro's number. Solving gives A = 32 amu.

All the Disintegrations of a Sample of an Unknown Nuclide