Lesson 3.1 & 3.2: Atomic Theory and Structure

Vocabulary flashcards covering basic chemical laws, Dalton's atomic theory, and the structure of the atom based on lecture notes.

Law of Conservation of Mass

States that matter is neither created nor destroyed during ordinary chemical reactions or physical changes.

Law of Definite Proportions

Explains the fact that a chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.

Law of Multiple Proportions

States that if two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.

John Dalton

Scientist who reasoned that elements were composed of atoms that combine in whole-number ratios, and turned Democritus's idea into a scientific theory testable by experiments by relating atoms to mass.

Democritus

Ancient thinker whose initial idea about atoms was turned into a testable scientific theory by John Dalton through relating atoms to the measurable property of mass.

Dalton's Atomic Theory

Theory stating that matter is composed of atoms, atoms of an element are identical in size, mass, and properties, atoms cannot be subdivided, created, or destroyed, atoms combine in simple whole-number ratios, and atoms are combined, separated, or rearranged in chemical reactions.

Isotopes

Atoms of an element that have different masses, serving as an example of an aspect of Dalton's theory that was modified rather than discarded.

Atom (Modern Definition)

The smallest particle of an element that retains the properties of that element.

Cathode Rays

Rays deflected by a magnetic field in the same manner as a wire carrying an electric current, which was known to have a negative charge.