What aspect of short lived radioactive substances make them a health hazard? What aspect of long lived radioactive substances make them a health hazard?

The disintegration constant of Technetium-99, an important medical tracer, is 10^-13 per second. Estimate the half-life of Technetium-99.

The activity of a radioactive sample depends on

1. the property of the radioactive MATERIAL and
2. the size of the SAMPLE.

The material is characterized by the disintegration (or "decay") constant which states what fraction of a sample will undergo the process per unit time.

For radiactive Carbon-14 the disintegration constant is equal to 3.84 x 10^-12 per second.

Based on that information, how many counts per minute would you expect for a mole of Carbon-14? Explain your answer. (Reminder: a mole consists of 6 x 10²³ items.)

The half-life of Carbon-14 is 5730 years. Living organisms, such as plants, continuously replenish Carbon-14 in their system from the atmosphere. After they die, the Carbon-14 content no longer is maintained. You are given a piece of wood whose Carbon-14 activity is 25% of what you observe in living wood. How long has the wood been dead? (Explain.)