HESI A2 - Nuclear Chemistry - Key Terms and Concepts

Nuclear Chemistry

The study of changes in the nucleus of an atom, including radioactive decay, fission, and fusion.

Radioactivity

The spontaneous emission of radiation from an unstable atomic nucleus.

Radioactive Decay

The process by which an unstable atomic nucleus loses energy by emitting radiation.

Alpha Particle

A type of radiation consisting of two protons and two neutrons, equivalent to a helium nucleus.

Beta Particle

A high-energy electron or positron emitted during beta decay.

Gamma Ray

High-energy electromagnetic radiation emitted during radioactive decay.

Half-Life

The time required for half of the radioactive atoms in a sample to decay.

Nuclear Fission

The splitting of a heavy nucleus into smaller nuclei, releasing a large amount of energy.

Nuclear Fusion

The combining of light nuclei to form a heavier nucleus, releasing energy.

Isotope

Atoms of the same element with different numbers of neutrons and different atomic masses.

Radioisotope

A radioactive isotope of an element.

Decay Series

A sequence of radioactive decays that a radioactive element undergoes to reach a stable form.

Transmutation

The conversion of one element into another through radioactive decay or nuclear reactions.

Chain Reaction

A self-sustaining series of nuclear fissions triggered by the release of neutrons.

Critical Mass

The minimum amount of fissile material needed to sustain a nuclear chain reaction.

Neutron Moderation

The process of slowing down neutrons to increase the likelihood of fission in a nuclear reactor.

Neutron Absorption

The process by which a nucleus captures a neutron, often leading to radioactive decay or fission.

Nuclear Reactor

A device used to control nuclear fission reactions to produce energy or radioactive isotopes.

Control Rods

Materials used in nuclear reactors to absorb neutrons and regulate the rate of fission.

Coolant

A substance used in nuclear reactors to remove heat generated by fission reactions.

Radiation

Energy emitted in the form of particles or waves from a radioactive source.

Ionizing Radiation

Radiation with enough energy to remove tightly bound electrons from atoms, creating ions.

Non-Ionizing Radiation

Radiation that does not have enough energy to remove electrons from atoms.

Geiger Counter

A device used to detect and measure ionizing radiation.

Scintillation Counter

A device used to detect radiation by measuring the light emitted when radiation interacts with a material.

Background Radiation

Low levels of radiation present in the environment from natural and artificial sources.

Radiation Dosimeter

A device used to measure an individual's exposure to ionizing radiation.

Radiation Shielding

Materials used to protect against harmful radiation, such as lead or concrete.

Nuclear Waste

Radioactive byproducts from nuclear reactors or other nuclear processes that require safe disposal.

Nuclear Medicine

The use of radioactive substances in medical diagnosis and treatment.

Radiopharmaceutical

A radioactive drug used in nuclear medicine for diagnosis or therapy.

Positron Emission Tomography (PET)

A medical imaging technique that uses radioactive tracers to visualize metabolic processes.

Radiotherapy

The use of high-energy radiation to treat cancer by destroying cancer cells.

Carbon Dating

A method of determining the age of ancient objects by measuring the decay of carbon-14.

Uranium Enrichment

The process of increasing the concentration of uranium-235 in uranium for use in nuclear reactors or weapons.

Plutonium-239

A fissile isotope of plutonium used in nuclear reactors and weapons.

Nuclear Fuel Cycle

The series of steps involved in producing, using, and disposing of nuclear fuel.

Nuclear Proliferation

The spread of nuclear weapons and technology to additional countries or groups.

Nuclear Non-Proliferation Treaty (NPT)

An international treaty aimed at preventing the spread of nuclear weapons.

Fusion Reactor

A theoretical device designed to harness energy from nuclear fusion reactions.

Thermonuclear Reaction

A nuclear fusion reaction that occurs at extremely high temperatures.

Radon Gas

A naturally occurring radioactive gas that can accumulate in buildings and pose health risks.

Radiation Sickness

Illness caused by exposure to high levels of ionizing radiation.

Breeder Reactor

A nuclear reactor that produces more fissile material than it consumes.

Nuclear Meltdown

A severe nuclear reactor accident where the reactor core overheats and melts.

Cherenkov Radiation

A blue glow emitted when charged particles travel through a medium faster than the speed of light in that medium.

Spent Fuel

Used nuclear fuel that is no longer efficient for energy production but remains radioactive.

Nuclear Cross-Section

A measure of the probability of a nuclear reaction occurring between a nucleus and a particle.

Neutron Activation Analysis

A technique used to determine the composition of materials by exposing them to neutrons and measuring the resulting radiation.

Nuclear Binding Energy

The energy required to split a nucleus into its individual protons and neutrons.

Alpha Decay

A type of radioactive decay where an unstable nucleus emits an alpha particle.

Beta Decay

A radioactive process where a neutron converts into a proton or vice versa, emitting a beta particle (electron or positron).

Gamma Decay

The release of high-energy gamma radiation (γ-rays) from an excited nucleus without changing its atomic number.

Mass Defect

The difference between the mass of a nucleus and the sum of its individual nucleons, related to binding energy.

Radioactive Decay Constant

A proportionality constant (λ) that defines the rate of radioactive decay of a substance.

Activity (Radioactivity)

The rate at which a radioactive substance undergoes decay, measured in becquerels (Bq).

Becquerel (Bq)

The SI unit of radioactivity, representing one decay event per second.

Gray (Gy)

The SI unit of absorbed radiation dose, equivalent to one joule of energy absorbed per kilogram of matter.