Nuclear Chemistry – Key Vocabulary

Vocabulary flashcards summarizing essential nuclear-chemistry terms from the lecture: decay concepts, dating techniques, and historical context.

Plutonium-236 (Pu-236)

A radioactive isotope discussed in class; undergoes alpha decay with a half-life of 2.86 years.

Alpha emitter

A nuclide that decays by releasing an alpha particle (⁴₂He nucleus).

Alpha particle

A charged particle composed of 2 protons and 2 neutrons (symbol ⁴₂He) emitted during alpha decay.

Half-life (t₁∕₂)

Time required for one-half of a radioactive sample to decay; related to λ by t₁∕₂ = 0.693 ⁄ λ.

Decay constant (λ, rate constant k)

Proportionality factor for first-order radioactive decay; λ = 0.693 ⁄ t₁∕₂ and has units of time⁻¹.

Integrated first-order decay law

N(t) = N₀ e^(−λt); relates remaining nuclei to initial amount and time.

First-order process (radioactivity)

A reaction whose rate is directly proportional to the number of undecayed nuclei present.

Decay rate (disintegrations · min⁻¹ · g⁻¹)

Experimental measure of radioactivity; counts nuclear disintegrations per minute per gram of carbon (or other element).

Radiocarbon dating

Technique that estimates the age of once-living matter by measuring residual ¹⁴C relative to ¹²C.

Carbon-14 (¹⁴C)

Radioactive isotope of carbon (t₁∕₂ ≈ 5 715 years) produced in the atmosphere and incorporated into living organisms.

Carbon-14 half-life

5 715 years—the period over which half of an initial ¹⁴C sample decays.

Beta decay

Radioactive process in which a nucleus emits a beta particle (electron or positron); e.g., ¹⁴C → ¹⁴N + β⁻.

Daughter nucleus

The nuclide formed after a radioactive parent nucleus decays (e.g., ²⁰⁶Pb from ²³⁸U).

Uranium–lead dating

Method for dating non-living geologic samples by comparing ²³⁸U to its daughter ²⁰⁶Pb.

Uranium-238 (²³⁸U)

Long-lived radioactive isotope that decays through a series to ²⁰⁶Pb; used in U–Pb dating.

Lead-206 (²⁰⁶Pb)

Stable daughter product of ²³⁸U decay; its ratio to uranium indicates sample age.

Fission

Splitting of a heavy nucleus into lighter nuclei with release of energy and neutrons; basis of atomic bombs and nuclear power.

Manhattan Project

WWII U.S. project that developed the first nuclear weapons using principles of fission.

Neutron capture

Process where a nucleus absorbs a neutron, often leading to an excited or heavier isotope (e.g., ²³⁸U + n → ²³⁹U).

Exponential decay equation

General expression N(t) = N₀ e^(−kt) describing the time-dependent decrease of a radioactive sample.