Evolution of Atomic Models and Basic Atomic Structure

Vocabulary flashcards covering the evolution of atomic models and the basic components and concepts of the atom, relevant to interpreting astronomical data.

Atom

The basic unit of matter; the smallest unit of an element that retains its identity, consisting of a nucleus and an electron cloud.

Nucleus

The dense, positively charged center of an atom containing protons and neutrons, accounting for most of the atom's mass.

Proton

Positively charged subatomic particle in the nucleus; determines the atomic number of an element.

Neutron

Electrically neutral subatomic particle in the nucleus; contributes to atomic mass and stability.

Electron

Negatively charged subatomic particle that orbits the nucleus and forms the electron cloud around the atom.

Electron cloud / Orbitals

Regions around the nucleus where electrons are most likely to be found, described by quantum mechanics as orbitals.

Atomic number

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

Mass number

The total number of protons and neutrons in the nucleus; roughly the atom’s mass.

Isotope

Atoms of the same element with different numbers of neutrons; same atomic number, different mass.

Dalton's model

Early view of the atom as a solid, indivisible sphere with no internal structure.

Thomson's plum pudding model

Atom modeled as a positively charged sphere with embedded electrons (plums in pudding).

Rutherford's nuclear model

Atom with a tiny, dense nucleus containing protons; electrons orbit around it—disproved the plum pudding model.

Bohr model

Electrons move in fixed energy levels around a small nucleus; transitions between levels involve photon emission/absorption (notably in hydrogen).

Quantum mechanical model

Current atomic model where electrons occupy probabilistic orbitals described by wave functions; no fixed paths.

Spectral lines

Specific wavelengths of light emitted or absorbed by atoms; used to identify elements in astronomical spectra.