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Questions and Answers
Questions and Answers
What type of radiation is emitted by unstable nuclei to become more stable?
What type of radiation is emitted by unstable nuclei to become more stable?
- Visible light
- Ultraviolet radiation
- Infrared radiation
- Alpha, beta and gamma radiation (correct)
Which type of radiation is the most ionizing?
Which type of radiation is the most ionizing?
- Beta radiation
- Gamma radiation
- All types of radiation are equally ionizing
- Alpha radiation (correct)
What happens to the mass number and atomic number when a radioactive nucleus emits a beta particle?
What happens to the mass number and atomic number when a radioactive nucleus emits a beta particle?
- The mass number decreases by 1 and the atomic number decreases by 1
- The mass number decreases by 1 and the atomic number increases by 2
- The mass number increases by 1 and the atomic number increases by 1
- The mass number remains the same and the atomic number increases by 1 (correct)
Which type of radiation is the most penetrating?
Which type of radiation is the most penetrating?
How can ionizing radiation be detected?
How can ionizing radiation be detected?
What is the purpose of measuring background radiation when detecting ionizing radiation?
What is the purpose of measuring background radiation when detecting ionizing radiation?
What is the primary measurement of the activity of a radioactive source?
What is the primary measurement of the activity of a radioactive source?
What is the key difference between contamination and irradiation of an object?
What is the key difference between contamination and irradiation of an object?
Which of the following is NOT a natural source of background radiation?
Which of the following is NOT a natural source of background radiation?
How does the activity of a radioactive source change over time?
How does the activity of a radioactive source change over time?
What is the purpose of using a radioactive tracer in medical diagnosis?
What is the purpose of using a radioactive tracer in medical diagnosis?
Which type of radiation is used to measure the thickness of metal sheets?
Which type of radiation is used to measure the thickness of metal sheets?
What is the primary danger of ionizing radiation to human cells?
What is the primary danger of ionizing radiation to human cells?
What is the purpose of using a radioactive source in a smoke detector?
What is the purpose of using a radioactive source in a smoke detector?
What causes atoms to become unstable and undergo radioactive decay?
What causes atoms to become unstable and undergo radioactive decay?
What is the difference between isotopes of the same element?
What is the difference between isotopes of the same element?
What does the atomic number of an atom represent?
What does the atomic number of an atom represent?
What does the mass number of an atom represent?
What does the mass number of an atom represent?
How are the mass number and atomic number of isotopes represented?
How are the mass number and atomic number of isotopes represented?
What type of radiation is emitted during radioactive decay?
What type of radiation is emitted during radioactive decay?
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Study Notes
Study Notes
Atomic Structure and Isotopes
- Atoms consist of a central nucleus surrounded by negatively charged electrons in electron orbitals.
- The nucleus is made up of protons and neutrons.
- The atomic number of an atom tells you the number of protons in the nucleus.
- The mass number tells you the total number of protons and neutrons.
- Isotopes are atoms of an element with the same atomic number but different mass numbers.
- Isotopes have the same number of protons but a different number of neutrons in their nucleus.
Radioactive Decay
- An imbalance of protons and neutrons causes atoms to become unstable and undergo radioactive decay.
- There are three types of radioactive decay: alpha, beta, and gamma.
- Unstable nuclei emit radioactive particles to become more stable.
Alpha Particles
- Alpha particles are made up of two protons and two neutrons.
- Alpha particles are identical to the nucleus of a helium atom.
- They are highly ionising and can cause ionisation by hitting other atoms and knocking electrons off them.
- Alpha particles are blocked by paper, skin, or a few centimeters of air.
- The emission of an alpha particle by a radioactive nucleus reduces the mass number by 4 and the atomic number by 2.
Beta Particles
- Beta particles are electrons emitted from an atom when a neutron turns into a proton.
- Beta particles are lighter than alpha particles and can travel further.
- They are moderately penetrating and can travel through paper but are blocked by a thin metal such as aluminum.
- Beta particles have a charge of -1 and are deflected away from an electric field.
- The emission of a beta particle by a radioactive nucleus increases the atomic number by 1 but does not change the mass number.
Gamma Radiation
- Gamma radiation is energy in the form of an electromagnetic wave.
- It occurs after a substance has undergone alpha or beta decay.
- Gamma radiation can only be blocked by a thick piece of lead or concrete.
- Gamma rays are weakly ionising and tend to pass through substances without knocking off electrons.
- Gamma radiation has no charge and is not deflected by an electric field.
Detecting Ionising Radiation
- Ionising radiation can be detected using a Geiger-Muller tube or photographic film.
- Geiger-Muller tubes measure the activity of a radioactive source by converting the number of radioactive particles into a count rate.
- Photographic film turns darker the longer it is exposed to radiation.
Background Radiation
- Background radiation is weak radiation that can be detected from external sources.
- Sources of background radiation include cosmic rays, radioactive rocks, plants, fallout from nuclear weapons testing, medical sources, and nuclear power plants.
Activity and Half-Life
- The activity of a radioactive source is the number of decays per unit time and is measured in becquerels.
- The activity of a radioactive source decreases over time.
- The half-life of a radioactive isotope is the time taken for half of the nucleus to decay or the time taken for the activity to halve.
- Half-life is different for different radioactive isotopes.
Uses of Radioactivity
- Smoke detectors use alpha emitters with a long half-life to detect smoke.
- Beta emitters are used to measure the thickness of metal sheets.
- Gamma emitters are used as tracers in medicine to diagnose diseases.
Contamination and Irradiation
- Contamination occurs when a radioactive substance physically touches an object.
- Irradiation occurs when a radioactive source is placed near an object and exposes it to its radiation without coming into contact with it.
Dangers of Ionising Radiation
- Ionising radiation can cause damage to human cells and tissues.
- Ionisation can result in DNA mutation, leading to cancer.
- Radioactive waste can remain radioactive for thousands of years and needs to be disposed of carefully.
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