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Aim: What is a half life of an element?

Aim: What is a half life of an element?. 212 Po 4 He +____. Do Now: Solve the following in your notes:. 142 Pm +____ 142 Nd. Half Life. The half-life is the amount of time it takes for half of the atoms in a sample to decay.

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Aim: What is a half life of an element?

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  1. Aim: What is a half life of an element? 212Po 4He +____ Do Now: Solve the following in your notes: 142Pm +____ 142Nd

  2. Half Life • The half-life is the amount of time it takes for half of the atoms in a sample to decay. • The half-life for a given isotope is always the same .

  3. Practice Problems • 1. The half-life of Th-227 is 18.2 day. How many days are required for 0.70 of a given • sample to decay? • 2. The half-life of Rn-222 is 3.823 day. What was the original mass of a sample of this • isotope if 0.0500 g remains after 7.646 day? • Try this yourself::::: • 3. The half-life of Pa-234 is 6.75 hr. How much (what fraction) of a sample of this • isotope remains after 20.25 hr?

  4. Homework # 5 1. Write nuclear equations for the following processes: • a. Ra-226 decays by α-emission. • b. The result of the β-decay of an isotope is Mg-22. • 2. Carbon-14 has a half-life of 5730 y. How much of a 144 g sample of carbon-14 will • remain after 1.719 × 104y? • 3. If the half-life of uranium-235 is 7.04 × 108 y and 12.5 g of uranium-235 remain after • 2.82 × 109 y, how much of the radioactive isotope was in the original sample?

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