Atomic Structure, Radiation, and Nuclear Reactions

Comprehensive practice flashcards covering atomic structure, radioactive decay, alpha, beta, and gamma radiation, background radiation, nuclear fission, and nuclear fusion.

Background radiation

Weak radiation that can be detected from natural and man-made sources in the environment.

Cosmic rays

A natural source of background radiation originating from outer space, contributing approximately $8\%$ to total background radiation.

Radiation from underground rocks

A natural source of terrestrial background radiation that contributes approximately $8\%$ to overall background exposure.

Nuclear fallout

A man-made source of background radiation resulting from past nuclear weapons testing or nuclear incidents.

Medical rays

A man-made source of background radiation (such as diagnostic X-rays) contributing approximately $15\%$ of total background radiation.

Radon

A radioactive gas originating naturally from rocks and soil that accounts for the largest proportion ($54\%$) of background radiation.

Internal radiation

Natural background radiation originating from radioactive isotopes within the human body, contributing approximately $11\%$ of total exposure.

Consumer products (radiation source)

A man-made source contributing approximately $3\%$ of the total background radiation dose.

Other sources of radiation

Minor miscellaneous sources accounting for approximately $1\%$ of total background radiation.

Sievert (Sv)

The standard scientific unit used for the measurement of radiation dose.

Chernobyl

A historical nuclear disaster site demonstrating how radioactive contamination can significantly increase local background radiation.

Factors affecting background radiation and dose

An individual's occupation and geographical location, both of which affect background radiation levels and radiation dose received.

Cellular effects of ionising radiation

Nuclear radiation ionises chemicals within the human body, altering cell behaviour and causing mutations that can lead to cancer.

Energy deposition tissue damage

The process by which nuclear radiation deposits large amounts of energy into bodily tissue, damaging or destroying cells completely.

Shielding (radiation protection)

A protective safety measure of placing absorbing barriers between a radioactive source and an individual to reduce the radiation dose received.

Exposure time limitation

A safety protocol of minimising the duration spent near a radioactive source to limit cumulative radiation dose.

Tongs (radiation handling)

A safety tool used to handle radioactive materials at a distance to minimise radiation exposure.

Contamination protective wear

Protective equipment including masks, gloves, and specialised clothing worn to prevent radioactive substances from getting onto or into the body.

Radiation badge

A wearable dose-monitoring badge that changes colour when exposed to high doses of radiation to measure personal exposure.

Short half-life

A radioactive property where a source has very high initial activity that quickly reduces to safe levels, presenting less long-term risk.

Long half-life

A radioactive property where a source remains weakly radioactive for a long duration, presenting a persistent risk that requires secure storage against contamination.

Timescale of half-lives

The span of half-life durations across different radioisotopes, which can range from fractions of a second to many thousands of years.

Radioactive decay

The spontaneous process in which unstable radioactive isotopes decay and emit nuclear radiation.

Random nature of radioactive decay

The principle that radioactive decay occurs without predictability, meaning one cannot forecast when an individual nucleus will disintegrate.

Activity

The rate of radioactive decay, defined as the number of disintegrations or counts per second, measured in becquerels ($\text{Bq}$).

Becquerel (Bq)

The scientific unit of radioactive activity, equal to one nuclear decay or count per second.

Count rate

The number of individual radiations detected by an instrument per second.

Half-life

The time taken for half of the radioactive nuclei in an unstable sample to decay, or for the activity to reach half of its original value.

Ionising radiation

High-energy nuclear radiation that interacts with neutral atoms or molecules by adding or removing electrons to produce ions.

Solid Sphere Model (Dalton, 1803)

The atomic model proposed by John Dalton in 1803 depicting the atom as a single, solid, indivisible particle.

Plum Pudding Model (Thomson, 1904)

The atomic model proposed by J.J. Thomson in 1904 following the discovery of the electron, picturing negative charges distributed inside a positive sphere.

Nuclear Model (Rutherford, 1911)

The atomic model proposed by Ernest Rutherford in 1911 showing that positive charge and mass are concentrated in a tiny central nucleus.

Alpha scattering off gold leaf

The 1911 experiment where alpha particles were directed at thin gold leaf; the observed deflections detected the existence of the atomic nucleus.

Shell Model (Bohr, 1913)

The atomic model proposed by Niels Bohr in 1913 describing electrons orbiting the nucleus in discrete shells to explain energy absorption and emission.

Modern atom model (Chadwick, 1932)

The atomic model finalized in 1932 when James Chadwick discovered the neutron, following the earlier discovery of protons in the nucleus.

Atomic empty space

The structural reality that atoms consist primarily of empty space surrounding a tiny, highly concentrated central nucleus.

Atomic nucleus

The tiny, dense central core of an atom composed of positively charged protons and neutral neutrons.

Electron shells

Concentric orbits or quantized energy levels surrounding the nucleus where electrons reside.

Electron shell transitions

The movement of electrons between energy shells caused by absorbing or emitting energy, often in the form of light.

Electrical neutrality of atoms

The neutral state of an atom where the total number of protons equals the total number of electrons.

Mass number

The total number of protons and neutrons contained within an atom's nucleus.

Atomic number

The proton number representing the total count of protons in a nucleus, which also equals the number of electrons in a neutral atom.

Calculation of neutron number

The arithmetic formula used to determine neutrons: $\text{Number of neutrons} = \text{Mass number} - \text{Proton number}$.

Proton

A subatomic particle located in the nucleus with a relative mass of $1$ and a positive electrical charge of $+1$.

Neutron

A subatomic particle located in the nucleus with a relative mass of $1$ and an electrical charge of $0$.

Electron

A subatomic particle orbiting the nucleus in shells with a relative mass of $0$ and a negative electrical charge of $-1$.

Ion

An electrically charged entity formed when a neutral atom gains or loses electrons, acquiring an overall negative or positive charge.

Isotopes

Atoms of the same chemical element that possess identical numbers of protons but different numbers of neutrons.

Irradiation

The process of exposing an object or body to nuclear radiation without radioactive material getting onto or into it.

Radioactive contamination

The unwanted presence of radioactive substances settling onto or getting inside an object or organism.

Balancing nuclear equations

The fundamental requirement that both total mass numbers and total atomic numbers balance equally on either side of the decay arrow.

Alpha particle nature

A form of nuclear radiation consisting of a helium nucleus ($^4_2\text{He}$) containing two protons and two neutrons.

Alpha particle speed

A relatively low speed of approximately $0.1c$ (ten percent of the speed of light).

Alpha particle range in air

A short travel range through air spanning approximately $3\text{--}5\,\text{cm}$.

Alpha particle charge

An overall positive electrical charge of $+2$.

Alpha particle penetration

Low penetrating ability, easily stopped and absorbed by a single sheet of paper or human skin.

Alpha particle ionising power

The strongest ionising capacity among alpha, beta, and gamma radiation types.

Alpha decay equation

The nuclear decay reaction represented by: $^A_Z\text{X} \rightarrow ^{A-4}_{Z-2}\text{Y} + ^4_2\text{He}$.

Beta particle nature

A form of nuclear radiation consisting of a fast-moving electron ($^0_{-1}\text{e}$) ejected from an unstable nucleus.

Beta particle speed

A medium speed of approximately $0.5c$ (half the speed of light).

Beta particle range in air

A medium travel range through air spanning approximately $0.5\text{--}1\,\text{m}$.

Beta particle charge

A negative electrical charge of $-1$.

Beta particle penetration

Medium penetrating ability, capable of penetrating skin and paper but stopped by a few millimetres of aluminium.

Beta particle ionising power

A medium ionising ability, intermediate between alpha particles and gamma rays.

Beta decay equation

The nuclear decay reaction represented by: $^A_Z\text{X} \rightarrow ^A_{Z+1}\text{Y} + ^0_{-1}\text{e}$.

Gamma ray nature

High-energy electromagnetic radiation emitted from an unstable nucleus carrying away surplus energy.

Gamma ray speed

The maximum physical speed, travelling precisely at the speed of light ($c$).

Gamma ray range in air

A long travel range through air extending over distances greater than a kilometre ($>\text{km}$).

Gamma ray charge

An electrical charge of $0$, as it consists of electromagnetic radiation rather than matter.

Gamma ray penetration

High penetrating ability, requiring thick lead or metres of concrete to absorb and reduce its intensity.

Gamma ray ionising power

The weakest ionising capability among alpha, beta, and gamma radiation types.

Nuclear effect of gamma emission

Causes no change to the mass number or atomic number of the parent nucleus, representing only a loss of surplus energy.

Smoke alarms (alpha use)

A domestic safety application utilizing an alpha source to ionise air, triggering an alarm when smoke interrupts the ionisation current.

Thickness monitoring of aluminium and paper (beta use)

An industrial control system where beta particles pass through rolled sheets to a detector, providing feedback to computer-controlled rollers.

Radiotherapy (gamma use)

A targeted medical application using penetrating gamma radiation to destroy cancerous cells.

Nuclear fission

The splitting of a large atomic nucleus into smaller daughter nuclei accompanied by the release of energy and neutrons.

Mass deficit in fission

The principle where the mass of the parent nucleus is greater than the combined mass of the resulting daughter nuclei.

$E = \Delta m c^2$ (in fission)

The mass-energy equivalence equation showing that lost mass is converted directly into energy released as radiation during fission.

Stimulated fission

An artificially induced nuclear split caused when a low-speed neutron is fired at and absorbed by a heavy nucleus such as Uranium-235 or plutonium.

Uranium-235

A fissile isotope utilized in nuclear reactor fuel that absorbs a neutron to trigger stimulated nuclear fission.

Uranium-236

The highly unstable intermediate nucleus formed when Uranium-235 absorbs a neutron, which promptly undergoes fission.

Fission neutrons

The $2$ or $3$ free neutrons ejected when an unstable heavy nucleus splits, capable of colliding with further uranium nuclei.

Fission chain reaction

A self-sustaining series of fission events where neutrons produced from initial splits trigger successive fissions in nearby nuclei.

Fuel rods

Rods in a nuclear reactor containing uranium fuel that split and release thermal energy when bombarded with neutrons.

Graphite moderator

A core component in a nuclear reactor that slows fast fission neutrons down to the correct speed required for fission.

Boron control rods

Neutron-absorbing rods in a nuclear reactor core that are inserted to reduce the rate of fission or removed to allow the rate to increase.

Nuclear reactor coolant

A fluid circulated through a nuclear reactor to transfer heat away from the core to produce steam to drive electricity-generating turbines.

Nuclear reactor waste

Spent reactor material that is intensely radioactive, hot, and possesses very long half-lives, requiring secure containment to prevent contamination.

Nuclear fusion

The process where two small atomic nuclei collide and fuse together to form a heavier nucleus, releasing large amounts of energy.

Mass deficit in fusion

The condition where the sum of the masses of the two initial nuclei is greater than the final mass of the combined heavier nucleus.

Natural fusion reactor

A star, such as our Sun, that naturally and continuously generates heat and light energy via nuclear fusion.

Net energy barrier in fusion

The current technological limitation wherein human-made fusion reactors consume at least as much energy as they produce, yielding no net energy release.

Proton repulsion in fusion

The electrostatic repulsive force between positive protons that requires nuclei to collide at extremely high speeds to undergo fusion.

Plasma temperature threshold for fusion

The extreme thermal condition of at least $150,000,000\,^{\circ}\text{C}$ required for hot gas or plasma to allow nuclear fusion to occur.

Fusion of Hydrogen-1 and Hydrogen-2

A specific fusion collision where a Hydrogen-1 nucleus and a Hydrogen-2 nucleus collide and fuse together to form Helium-3.

Nuclear stability ratio

The fundamental requirement that stable atomic nuclei must maintain a correct ratio of protons and neutrons.

Neutron proportion in heavy nuclei

The physical rule that the heavier an atomic nucleus is, the greater the proportion of neutrons it requires to be stable.

Fusing tendency of light nuclei

The natural tendency of atomic nuclei lighter than iron to fuse together to achieve a more stable configuration.

Fission tendency of heavy nuclei

The natural tendency of atomic nuclei heavier than iron to undergo nuclear fission to become more stable.

Iron-56

The most stable atomic nucleus; nuclei lighter than it tend to fuse, whereas nuclei heavier than it tend to split via fission.