Introduction to Nuclear Reactions and Radioactivity

Vocabulary flashcards covering nuclear reactions, isotopes, radioactive decay, and radiation characteristics based on the lecture notes.

Nuclear Fission

The splitting of a heavy nucleus into lighter nuclei, releasing energy and producing relatively less‐radioactive products; basis of nuclear power plants and some weapons.

Nuclear Fusion

The combination of two light nuclei to form a heavier nucleus, releasing large amounts of energy with minimal nuclear waste.

Deuterium (²H)

An isotope of hydrogen with one proton and one neutron in the nucleus.

Tritium (³H)

A radioactive isotope of hydrogen containing one proton and two neutrons.

Helium-4 (⁴He)

A stable nucleus of two protons and two neutrons; also the typical product of nuclear fusion and alpha decay.

Neutron

An electrically neutral nucleon found in the nucleus; contributes to mass number but not atomic number.

Proton

A positively charged nucleon found in the nucleus; its count equals the atomic number of an element.

Nucleon

Collective term for protons and neutrons inside an atomic nucleus.

Atomic Number (Z)

The number of protons in the nucleus of an atom; defines the element’s identity.

Mass Number (A)

The total number of protons and neutrons (nucleons) in an atomic nucleus.

Neutron Number (N)

The number of neutrons in a nucleus, calculated by N = A − Z.

Isotope

Atoms of the same element (same Z) that differ in mass number (A) due to different numbers of neutrons.

Protium

The most common hydrogen isotope, containing one proton and no neutrons.

Nuclear Notation

Symbolic representation of nuclides written as ⁸₄Be or AZX, where A = mass number and Z = atomic number.

Transmutation

The conversion of one element into another through nuclear decay or bombardment processes.

Radioactive Decay

Spontaneous transformation of an unstable nucleus into a more stable nucleus with emission of particles or radiation.

Parent Nucleus

The original unstable nuclide that undergoes radioactive decay.

Daughter Nucleus

The product nuclide(s) formed after a radioactive decay process.

Ionizing Radiation

Radiation energetic enough to remove electrons from atoms it encounters, creating ions.

Alpha Particle (⁴₂He or α)

A helium-4 nucleus (2 protons, 2 neutrons) emitted during alpha decay; carries +2 charge and low penetration.

Beta Particle (β⁻)

A high-speed electron (⁰₋₁e) emitted during beta-minus decay; carries ‑1 charge and moderate penetration.

Positron (β⁺)

The antimatter counterpart of the electron (⁰₊₁e) emitted in beta-plus (positron) decay; carries +1 charge.

Gamma Ray (γ)

High-energy electromagnetic radiation (⁰₀γ) emitted from an excited nucleus; no mass or charge, highly penetrating.

Alpha Decay

A nuclear reaction where a nucleus emits an alpha particle, decreasing A by 4 and Z by 2.

Beta-Minus Decay

Radioactive process in which a neutron converts to a proton and an electron, increasing Z by 1 while A remains unchanged.

Beta-Plus Decay (Positron Emission)

Process in which a proton converts to a neutron and a positron, decreasing Z by 1 with no change in A.

Electron Capture

A nucleus captures an inner-shell electron (⁰₋₁e), converting a proton into a neutron and lowering Z by 1.

Gamma Decay

Emission of a gamma photon from an excited nucleus; A and Z remain unchanged.

Penetrating Ability

Relative capacity of radiation to pass through matter: α stopped by paper, β by aluminum foil, γ requires thick lead or concrete.

Electromagnetic Spectrum

Range of electromagnetic radiation from low-energy radio waves to high-energy gamma rays; ionizing radiation includes UV, X-rays, and γ-rays.

Nuclear Transmutation Reaction

An induced nuclear reaction where a nucleus is struck by a particle (e.g., α, n, p) to form a heavier nucleus.

Nuclear Decay Reaction

Natural process in which an unstable nucleus emits radiation and transforms into a different nucleus.

Bombardment (e.g., ⁹₄Be + ⁴₂α) / Nuclear Reaction

The collision of a nucleus with a subatomic particle (often α, p, or n) to produce new nuclei and particles.

Parent vs. Daughter Isotopes

Terms describing the initial (parent) and resulting (daughter) nuclides in a radioactive decay sequence.

Matter–Antimatter Pair

Particles with identical mass but opposite charge and quantum numbers, such as electron–positron or proton–antiproton.

Ionizing vs. Non-Ionizing Radiation

Classification where ionizing radiation (UV, X-ray, γ) can remove electrons, whereas non-ionizing (radio, microwave) cannot.

Smoke-Detector Application

Alpha particles ionize air molecules, maintaining a current; smoke interrupts the ion flow, triggering the alarm.

Beta Particle Hazard

Because β particles are lighter and faster than α, they penetrate skin more deeply and can damage internal tissues if ingested or inhaled.

Gamma Ray Shielding

Requires dense materials like thick lead or concrete due to high energy and penetration depth.