# Worksheet: Radioactive Half-Lives

In this worksheet, we will practice using measurements of activity or isotope ratios to calculate the half-lives and decay constants of unstable nuclei.

**Q2: **

Radon-222 decays by emission and is one of the largest sources of radiation exposure for many people.

Write a balanced equation for the decay of radon-222.

- A
- B
- C
- D
- E

After 12.7 days, 90.0% of a sample of radon-222 has decayed. Calculate the half-life for the decay process.

Radon-222 is most hazardous if inhaled. Which properties of particles are responsible for this effect?

- AIt is strongly penetrating and strongly reducing.
- BIt is weakly penetrating and weakly oxidizing.
- CIt is weakly penetrating but strongly ionizing.
- DIt is strongly penetrating but weakly oxidizing.
- EIt is strongly penetrating but weakly ionizing.

**Q3: **

What is the half-life of a radioactive material?

- AHalf of the time taken for all of the nuclei to decay
- BThe inverse of the rate constant for the decay process
- CThe time taken for half of the nuclei to decay
- DThe average time taken for nuclei to decay
- EHalf of the average time taken for nuclei to decay

**Q12: **

What is the half-life of a radioactive material in terms of the rate constant for the radioactive decay, ?

- A
- B
- C
- D
- E