Chemistry Unit 2: Matter, Atomic Theory, and Radioactivity

Vocabulary flashcards covering types of matter, properties, separation methods, the history of atomic theory, and types of radioactive decay based on lecture notes.

Matter

Anything that has mass and takes up space.

Pure substance

Matter with a fixed composition.

Element

A substance made of one type of atom.

Compound

Two or more elements chemically bonded.

Mixture

Substances physically combined and not chemically bonded together.

Heterogenous mixture

A mixture that is not evenly mixed, where different parts can be seen.

Homogenous mixture

A mixture that is evenly mixed throughout.

Solution

A homogenous mixture.

Methods of separation

Techniques used to separate mixtures, including filtration, evaporation, chromatography, distillation, magnetism, and decanting.

Physical Properties

Properties observed where the substance stays the same, such as color, density, melting point, boiling point, mass, volume, conductivity, and state of matter (solid, liquids, gas).

Chemical Properties

Properties observed where a new substance forms, such as flammability, ability to rust, reactivity with acids, and ability to tarnish.

Democritus

Proposed the idea (not a conclusion) that matter is made of tiny indivisible particles called atomos.

John Dalton

Proposed that matter is made of atoms: 1) All matter is made of atoms; 2) Atoms of the same element are identical in mass and properties; 3) Atoms of different elements differ in their properties; 4) Atoms combine in simple number ratios to form compounds.

J.J. Thompson

Scientist who used cathode ray experiments to discover the electron and proposed the plum pudding model.

Ernest Rutherford

Scientist whose gold foil experiment showed that atoms are mostly empty space with a tiny, dense, positively charged nucleus.

Niels Bohr

Scientist who proposed that electrons occupy energy levels around the nucleus.

Erwin Schrodinger

Helped develop the quantum mechanical model, proposing that electrons reside in orbitals rather than fixed circular paths.

James Chadwick

Scientist who discovered the neutron, a neutral particle found in the nucleus.

Radioactivity

The process or property of unstable nuclei emitting radiation.

Alpha Decay

A form of radioactive emission stopped by paper or the outer layer of skin.

Beta Decay

A form of radioactive emission stopped by a sheet of metal, such as aluminum.

Gamma Ray

High-energy radiation that requires substantial shielding, such as thick lead or concrete.