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.

Test your knowledge on radioactivity, types of radioactive decay (alpha, beta, gamma), atomic structure, and isotopes. Learn about how atoms become unstable and undergo radioactive decay due to an imbalance of protons and neutrons.