Neutron Capture & Atomic Structure Vocabulary

30 vocabulary flashcards summarizing neutron-capture nucleosynthesis, historical atomic models, and key subatomic concepts.

Neutron Capture

Process in which a nucleus absorbs one or more neutrons, creating a heavier isotope and enabling formation of elements heavier than iron.

s-Process (Slow Neutron Capture)

Neutron capture that occurs over hundreds or thousands of years, allowing beta decay between captures and producing stable isotopes up to lead inside stars before they explode.

r-Process (Rapid Neutron Capture)

Neutron capture that happens in fractions of a second during stellar explosions, adding many neutrons before beta decay and creating very heavy, neutron-rich isotopes.

Beta Decay

Radioactive decay in which a nucleus emits an electron (β-particle), converting a neutron to a proton and shifting the element one place up the periodic table.

Isotope

Atoms of the same element that contain the same number of protons but different numbers of neutrons, giving them different atomic masses.

John Dalton

British chemist (1766–1844) who published the first modern atomic theory and introduced an early table of elements.

Dalton’s Atomic Theory

1803 proposal stating that matter is composed of indivisible atoms, atoms of each element are identical, atoms of different elements differ, and chemical reactions rearrange but do not destroy atoms.

Joseph John Thomson

Physicist who discovered the electron through the Cathode Ray Tube experiment and proposed the Plum Pudding model of the atom.

Cathode Ray Tube (CRT) Experiment

Thomson’s apparatus with a vacuum tube, cathode (–), anode (+), and fluorescent screen that showed negatively charged beams, leading to the discovery of electrons.

Electron

Subatomic particle with a negative charge, very small mass, and ability to move between atoms; orbits the nucleus in shells.

Plum Pudding Model

Thomson’s atomic model describing electrons embedded in a diffuse positively charged “pudding.”

Ernest Rutherford

New Zealand-born physicist who proposed the nuclear (planetary) model of the atom after the Gold Foil experiment.

Gold Foil Experiment

Rutherford’s test in which alpha particles were scattered by thin gold foil, revealing a small, dense, positively charged nucleus and largely empty atomic space.

Planetary (Nuclear) Model

Rutherford’s depiction of an atom with electrons orbiting a central, dense, positively charged nucleus, similar to planets around the Sun.

Nucleus

Tiny, dense core of an atom containing protons and neutrons and holding nearly all the atom’s mass.

Alpha Particle

Positively charged particle (2 protons + 2 neutrons) emitted in radioactive decay and used by Rutherford to probe atomic structure.

Proton

Positively charged subatomic particle located in the nucleus; its count equals the atomic number of an element.

Neutron

Electrically neutral subatomic particle found in the nucleus; contributes to atomic mass and isotopic variation.

Atomic Number (Z)

Number of protons in an atom’s nucleus; also equals the number of electrons in a neutral atom.

Atomic Mass (Mass Number, A)

Total number of protons plus neutrons in an atom’s nucleus.

Number of Neutrons Formula

n = Atomic Mass (A) – Atomic Number (Z).

Niels Bohr

Physicist who refined Rutherford’s model by introducing quantized electron orbits in 1915.

Bohr Model

Atomic model with electrons moving in discrete circular orbits (shells) around the nucleus, each with fixed energy.

Orbital Shell

Specific, quantized path in which an electron orbits the nucleus; farther shells hold higher energy electrons.

Quantum Number (n)

Positive integer (n=1,2,3…) labeling an electron’s energy level or shell in the Bohr model (K, L, M, N…).

Ground State

Lowest-energy configuration of electrons in an atom, with electrons occupying the closest possible shells.

Energy Absorption (Excitation)

Process in which an electron gains energy and jumps from a lower to a higher orbital shell.

Energy Emission (Relaxation)

Process in which an electron loses energy and falls from a higher to a lower orbital shell, often emitting light.

Subatomic Particles

Collective term for electrons, protons, and neutrons that make up an atom.

Neutron-Rich Isotope

Isotope containing more neutrons than stable forms, often produced in the r-process and prone to radioactive decay.