1. Nuclear Chemistry: Half-Life

2. Half Life Definition = time it takes for half of a radioactive sample to decay; describes rate of decay The stability of the isotope is what determines the rate of decay. Less Stable = faster decay

3. Half-Life After each half-life, half of the sample decays. Start = 100% – 40 blue particles are present 1 half-life = 50% – 20 blue remain 2 half-lives = 25% – 10 blue remain 3 half-lives = 12.5% – 5 blue remain 4 half-lives = 6.25% – 2.5 blue remain

4. Half-Life Amount never becomes zero After 10 half-lives sample considered nonradioactive because it approaches the level of background radiation. Because the amount never reaches zero, radioactive waste disposal and storage causes problems. Would you want radioactive waste in your community?