Isotopes and Radioactivity

What happens when the number of protons in an atom changes?

• It becomes a completely different atom, with different properties

• Usually nothing happens, unless the atom is radioactive

• The number of electrons changes too

• The atomic nucleus explodes

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How can radioactivity be useful? =

• It can be used to microwave food

• It can be used in cancer treatments and pacemakers

• It can be used to create helpful gamma rays

• It can be used to create radioactive waste

A radioactive isotope is a substance that

• will eventually gain electrons through bonding

• will become stable by cooling down

• is unstable and will 'decay' by losing particles

• is not found naturally on the Earth

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When Uranium decays it emits an alpha particle, forming an isotope of Thorium. Which of the above decay equations is correct?

• A

• B

• C

• D

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In the above decay equation, what are the missing numbers x and y?

• A

• B

• C

• D

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The half-life of a substance is

• the amount of substance left after it has decayed

• the time it takes for half of the isotope to decay

• the time it takes for half the mass to have radiated away

• the mass of half of the isotope after decaying

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The activity of an isotope is

• the number of particles/rays emitted per second

• the same as the half-life in seconds

• the amount of radiation emitted over the lifespan of the isotope

• the amount of heat generated per second

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Which of the above graphs shows how the activity of a sample varies with time?

• A

• B

• C

• D

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A sample of 16 g of radioactive substance X has a half-life of 2 hours. What percentage of the sample is left after 6 hours?

• none

• 12.5 %

• 25 %

• 33.3 %

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Two isotopes of the same element have

• the same number of protons but different numbers of neutrons

• the same number of protons but different numbers of electrons

• the same number of neutrons but different numbers of protons

• the same number of electrons but different numbers of protons

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