Radioactivity and Atomic Structure Quiz

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.