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Questions and Answers
Radioactivity was discovered by Pierre Curie.
Radioactivity was discovered by Pierre Curie.
False
Alpha particles consist of two protons and two neutrons.
Alpha particles consist of two protons and two neutrons.
True
Beta particles are slower and have a lower penetrating power than alpha particles.
Beta particles are slower and have a lower penetrating power than alpha particles.
False
Carbon-14 is utilized in carbon dating and emits beta particles.
Carbon-14 is utilized in carbon dating and emits beta particles.
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Gamma radiation is affected by electric and magnetic fields.
Gamma radiation is affected by electric and magnetic fields.
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Alpha particles can penetrate bricks and metal easily.
Alpha particles can penetrate bricks and metal easily.
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Henri Becquerel's experiment involved placing uranium salts in sunlight.
Henri Becquerel's experiment involved placing uranium salts in sunlight.
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Gamma radiation is a form of high energy electromagnetic radiation.
Gamma radiation is a form of high energy electromagnetic radiation.
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Gamma rays are the least dangerous type of radiation.
Gamma rays are the least dangerous type of radiation.
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In a nuclear reaction, new elements can be formed.
In a nuclear reaction, new elements can be formed.
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Chemical reactions primarily involve changes in the nucleus of atoms.
Chemical reactions primarily involve changes in the nucleus of atoms.
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The half-life of Carbon-14 is 5730 days.
The half-life of Carbon-14 is 5730 days.
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Half-life measures the time taken for half of the nuclei in a sample to decay.
Half-life measures the time taken for half of the nuclei in a sample to decay.
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Nuclear radiation is released during chemical reactions.
Nuclear radiation is released during chemical reactions.
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After 5730 years, starting with 10g of Carbon-14, only 2.5g will remain.
After 5730 years, starting with 10g of Carbon-14, only 2.5g will remain.
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Nuclear reactions result in broken chemical bonds.
Nuclear reactions result in broken chemical bonds.
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After 5730 years, half of a 2.5g sample of Carbon-14 will decay to 1.25g of Carbon-14.
After 5730 years, half of a 2.5g sample of Carbon-14 will decay to 1.25g of Carbon-14.
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Iodine-131 is used primarily to kill germs in hospitals.
Iodine-131 is used primarily to kill germs in hospitals.
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Radiocarbon dating can help determine the age of animal bones by analyzing the Carbon-12 to Carbon-14 ratio.
Radiocarbon dating can help determine the age of animal bones by analyzing the Carbon-12 to Carbon-14 ratio.
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Caesium-137 has a half-life of 30 years.
Caesium-137 has a half-life of 30 years.
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Beta particles have a positive charge and significant mass.
Beta particles have a positive charge and significant mass.
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The process of food irradiation involves treating food with beta particles.
The process of food irradiation involves treating food with beta particles.
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Smoke alarms utilize Americium-241 to detect smoke.
Smoke alarms utilize Americium-241 to detect smoke.
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Radioactivity refers to the spontaneous random decay of a nucleus that produces only alpha particles.
Radioactivity refers to the spontaneous random decay of a nucleus that produces only alpha particles.
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Study Notes
History of Radioactivity
- Radioactivity was discovered by Henri Becquerel, a French physicist.
- He was studying the effect of sunlight on uranium salts.
- He left some uranium salts on a photographic plate, wrapped in black paper.
- The plate became fogged near the uranium salt.
- This indicated that the uranium salt was emitting radiation that penetrated the black paper.
- Pierre and Marie Curie further investigated this phenomenon.
- They isolated polonium and radium from a uranium ore called pitchblende.
Nature of Radioactive Radiation
- Three types of radiation were discovered based on how they behaved in electric and magnetic fields.
- Alpha particles are groups of two protons and two neutrons bound together.
- Alpha particles carry a double positive charge (2+). They can be represented as ⁴₂He
- Alpha particles are emitted from unstable nuclei of radioactive elements.
- They're relatively large, travel slowly, and have low penetrating power. Stopped by a few cm of air or paper.
- Alpha decay changes the nucleus to a more stable one. Example: ²³⁸₉₂U → ⁴₂He + ²³⁴₉₀Th
- Beta particles are fast-moving electrons.
- They form when a neutron in an unstable nucleus changes to a proton and an electron.
- The electron is ejected from the nucleus. Example: ¹⁴₆C → ¹⁴₇N + ⁰₋₁e
- Beta particles are lighter than alpha particles, travel faster, and have a higher penetrating power. Stopped by thin sheets of metal.
- Gamma radiation: high energy electromagnetic radiation.
- It doesn't consist of charged particles, so it's not deflected by electric or magnetic fields.
- It has very high penetrating power and can penetrate bricks and metal. Stopped only by thick slabs of lead.
Nuclear Reactions
- A nuclear reaction alters the composition, structure, or energy of an atomic nucleus.
- Chemical reactions change electron sharing/transfer, while nuclear reactions change the nucleus.
| Feature | Chemical Reaction | Nuclear Reaction |
|---|---|---|
| What changes | Electrons | Nucleus and electrons |
| Element formed | No new element | New element formed |
| Radiation | No nuclear radiation | Nuclear radiation released |
| Bonds | Chemical bonds broken/formed | No chemical bond breaking/forming |
Half-Life
- Half-life is the time it takes for half of the nuclei in a given sample to decay.
- Radioactive isotopes decay at their own rates.
- Scientists use half-life to compare decay rates of isotopes.
Uses of Radioisotopes
- Medical: Gamma rays can kill cancerous cells, sterilize instruments. Iodine-131 measures iodine uptake in the thyroid.
- Archaeological: Radiocarbon dating determines the age of objects containing carbon by measuring the ratio of Carbon-14 to Carbon-12.
- Agricultural: Studying fertiliser uptake in plants.
- Food irradiation: Killing disease-carrying organisms in food.
- Smoke alarms: Americium-241 detects smoke.
Exam Questions (Examples)
- 2013 Question 10: Defines radioactivity, differences between chemical and nuclear reactions, properties of beta particles, and fraction of a radioactive isotope remaining after a certain time.
- 2011 Question 10: Defines isotopes, radioactivity, radioisotopes, and describes the beta decay of Carbon-14. Also explains changing isotope ratios over time.
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Description
Explore the fascinating history and nature of radioactivity, from its discovery by Henri Becquerel to the work of the Curies. Learn about the various types of radiation, particularly alpha particles, and their properties. This quiz delves into the fundamental concepts and discoveries that paved the way for modern physics.
