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A set of vocabulary flashcards covering fundamental ideas from the lecture: particle theory, phases of matter, subatomic particles, key historical atomic models, and related atomic properties.
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Particle Theory of Matter
States that: (1) all matter is composed of tiny particles; (2) particles of the same substance are identical regardless of state; (3) particles attract each other; (4) spaces between particles are large compared with particle size; (5) particles are in constant motion.
Matter
Anything that occupies space and has mass; composed of atoms and molecules and exists in solid, liquid, and gas phases.
Atom
The smallest unit of an element that retains the element’s properties; originally thought to be indivisible and solid in Dalton’s model.
Subatomic Particle
Particles that make up the atom—protons, neutrons, and electrons.
Proton
Positively charged (+) subatomic particle located in the nucleus; contributes to atomic mass.
Neutron
Neutral subatomic particle found in the nucleus; adds mass but carries no charge.
Electron
Negatively charged (–) subatomic particle that occupies specific energy levels (orbits) around the nucleus.
Nucleus
Tiny, dense, positively charged core of an atom containing protons and neutrons; most of the atom’s mass resides here.
Energy Level (Orbit)
Fixed region around the nucleus where an electron is likely to be found; each has a specific size and energy.
Electron Transition
Movement of an electron between energy levels: it moves outward when it gains energy and inward when it loses energy.
Solid Sphere Model (Dalton, 1803)
Early atomic model describing the atom as an indivisible, solid sphere with unique properties for each element.
Plum Pudding Model (J. J. Thomson, 1904)
Model portraying the atom as an electrically neutral sphere of positive charge with embedded negative electrons.
Nuclear Model (Ernest Rutherford, 1911)
Model that introduced a central nucleus: atoms are mostly empty space with electrons outside the dense, positive nucleus.
Planetary/Bohr Model (Niels Bohr, 1913)
Model in which electrons travel in fixed circular orbits around the nucleus, each orbit having quantized energy.
Intermolecular (Particle) Attraction
Force that causes particles to attract one another; strength affects a substance’s state and physical behavior.
Compound Formation
Process in which atoms of different elements chemically combine, forming substances with new properties.
Atomic Neutrality
Condition in which an atom’s total positive charge equals its total negative charge, resulting in no overall charge.
Indivisibility Postulate
Dalton’s assertion that atoms cannot be subdivided, created, or destroyed in chemical reactions.