Define (i) radioactivity; (ii) the half-life of a radioactive isotope - Leaving Cert Chemistry - Question b - 2010
Question b
Define (i) radioactivity; (ii) the half-life of a radioactive isotope.
Americium-241 is a radioactive isotope used in domestic smoke detectors. Americium-241 has a ... show full transcript
Worked Solution & Example Answer:Define (i) radioactivity; (ii) the half-life of a radioactive isotope - Leaving Cert Chemistry - Question b - 2010
Step 1
Define (i) radioactivity
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Answer
Radioactivity is the spontaneous random decay of a nucleus through disintegration or decomposition, releasing radiation such as alpha, beta, or gamma rays.
Step 2
Define (ii) the half-life of a radioactive isotope
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Answer
The half-life is the time taken for half of the radioactive isotopes in a sample to decay. This is often expressed mathematically as:
t1/2=λln(2)
where ( \lambda ) is the decay constant.
Step 3
Determine the value of A and the value of Z
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Answer
From the equation:
\text{\textsuperscript{241}_{95}Am \rightarrow \textsuperscript{237}_{93}Np + \textsuperscript{4}_{2}He + energy}
The value of A (mass number) is 237 for neptunium (Np).
The value of Z (atomic number) is 93 for neptunium (Np).
Step 4
State one risk associated with exposure to alpha radiation
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Alpha particles can cause ionization in human cells, leading to DNA damage and an increased risk of cancer.
Step 5
Explain why occupants are not at risk from alpha radiation
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Occupants are not at risk from alpha radiation emitted by smoke detectors because alpha particles have low penetration power and cannot penetrate the skin. Additionally, they cannot travel far in air, reducing exposure risk.
Step 6
Explain whether americium-241 needs to be replaced regularly
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Americium-241 does not need to be replaced regularly since its half-life is over 400 years, meaning it decays very slowly and maintains its activity for a long time. As a result, smoke detectors can function properly for many years without the need for replacement of the americium-241.
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