Radioactivity and Half-Life

What is a half-life?

• the time required for one half of the radioactive atoms in a sample to decay

• the time required for one third of the radioactive atoms in a sample to decay

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What is a Geiger counter?

• an instrument that uses sonar to bounce sound waves off the ocean bottom

• an instrument that measures vibrations in the ground

• an instrument that detects the particles emitted or given off by decaying atoms

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When the radioactive atoms in a sample decay by half...

• alpha decay

• Beta decay

• half-life

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Uranium238 take _________________for one half-life.

• 5730 years

• 20 billion

• 1.65 million

• 4.5 billion

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The time it takes for 50% of the nuclei in a radioactive sample to decay to its stable isotope is called _____

• the daughter product

• geologic time

• the half-life

• the half-time

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Half-life

• A measurement of the total number of protons and neutrons in an element

• atoms of the same element with different numbers of neutrons

• The spontaneous release of material from the nucleus of radioactive isotopes

• The time it takes for 1/2 of an original radioactive atom to decay

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How long is one half life of C-14

• 5730

• 11460

• 17190

• 28650

After 2 half lives, what percent is the parent isotope?

• 100%

• 50%

• 75%

• 25%

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After 4 half-lives, 1g of a sample of Krypton-85 remains unchanged.  What was the original mass of the sample?

• 16g

• 32g

• 0.0625g

• 4g

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If one has 12 kg of Polonium and it undergoes two half-lives, how much do you have left?

• 12 kg

• 3 kg

• 6 kg

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