Radioactivity, Nuclear Reactions, and Decay Modes

Vocabulary flashcards covering key nuclear chemistry terms including radioactive decay modes, radiation types, half-life, nuclear fission, and fusion.

Radioactive Decay (Radioactivity)

The spontaneous disintegration of an atomic nucleus accompanied by the emission of particles, electromagnetic radiation, or both.

Some nuclei are inherently unstable due to the imbalance of protons and neutrons, leading them to release energy in the form of radiation as they reach a more stable state.

The only way for one element to be transformed into another (transmutation)

Nucleons

The subatomic particles located inside the nucleus, specifically protons and neutrons.

Nuclide

Any specific atom identified by its nuclear composition, represented either by nuclear symbol notation (such as $^{133}_{55}\text{Cs}$) or hyphen notation (such as $\text{cesium-133}$).

Transmutation

The transformation of an atom of one chemical element into an atom of a different chemical element through nuclear decay or reaction.

Alpha Particle

A helium nucleus ($^4_2\text{He}^{2+}$ or $\alpha$) consisting of $2$ protons and $2$ neutrons, possessing a mass number of $4$ and an atomic number of $2$. Has no electrons, so it is called a double positive.

Alpha Decay

A nuclear decay mode where an unstable nucleus emits an alpha particle, reducing its mass number by $4$ and atomic number by $2$; can be stopped by a piece of paper. Low penetrating Power

Beta Particle

A high-energy electron ($^0_{-1}e$ or $\beta$) ejected from the nucleus during decay, having a mass number of $0$ and a charge of $-1$. No protons

Beta Decay

A decay mode resulting from a neutron splitting into a proton and an electron; increases the atomic number by $1$ while leaving the mass number unchanged, and can be blocked by lead or glass mid penetrating power

Gamma Ray ($\gamma$)

High-energy electromagnetic radiation released during nuclear rearrangement; possesses no mass or charge and does not alter atomic or mass numbers. can be stopped by concrete, much thicker things.

Positron

An antimatter particle ($^0_{+1}e$ or $\beta^+$) with a mass number of $0$ (identical to an electron) and a charge of $+1$.

Positron Emission

A nuclear conversion process where a proton in an unstable nucleus transforms into a neutron and a positron; decreases the atomic number by $1$ while the mass number remains unchanged.

Electron Capture

A process in which an inner electron is captured by the nucleus and combines with a proton to form a neutron, decreasing the atomic number by $1$ while mass number stays unchanged.

Antimatter

A particle that exhibits properties (such as charge) opposite to those of an equivalent ordinary matter particle.

Half-Life ($t_{1/2}$)

The amount of time required for one-half of the radioactive nuclei in a given sample to undergo decay.

Big range in half lives from seconds to years

Decay Curve

A diagram or graph showing the progressive decay of a radioactive isotope sample over time. (log)

Nuclear Fission

The splitting of a heavy, unstable nucleus into smaller, medium-mass stable nuclei, accompanied by the release of energy and fast-moving neutrons.

energy is released along with neutrons

Chain Reaction

A self-sustaining nuclear process where neutrons emitted during fission strike and split adjacent heavy nuclei.

used in nuclear reactors and weapons

Nuclear Fusion

The combining of two small, low-mass nuclei to form a heavier nucleus, releasing massive amounts of energy and requiring temperatures around $100{,}000{,}000\,^\circ\text{C}$ to overcome electrostatic repulsion.

Real life examples

• carbon dating using half life

• radiation treatment for cancer

• nuclear power plants generating electrical energy

• sterilization of medical tools

• power for space travel

• radioactive tracers for medical diagnostic procedures