Atoms, Molecules, and Ions

These flashcards cover key terms and concepts related to atoms, molecules, and ions as discussed in the lecture notes.

Atomic Theory of Matter

The theory that matter is composed of discrete units called atoms, described historically by philosophers and later formalized by scientists like John Dalton.

Law of Constant Composition

The principle stating that a given chemical compound always contains its component elements in fixed ratio by mass.

Postulates of Dalton’s Atomic Theory

A set of four principles proposed by John Dalton that describe the nature of atoms and their behavior in chemical reactions.

Law of Conservation of Mass

The principle stating that mass is neither created nor destroyed in a chemical reaction; the total mass before and after the reaction remains the same.

Electron

A negatively charged subatomic particle found in the outer regions of an atom.

Cathode Ray Tube

An experimental apparatus that demonstrates the properties of electrons, leading to their discovery by J.J. Thomson.

Millikan Oil-Drop Experiment

An experiment by Robert Millikan that measured the charge of an electron by observing oil droplets in an electric field.

Radioactivity

The spontaneous emission of high-energy radiation from unstable atomic nuclei, first observed by Henri Becquerel.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Chemical Formula

A representation of a substance using symbols for its constituent elements and numbers to indicate the ratio of these elements.

Ionic Compound

A compound formed from the electrostatic attraction between cations and anions.

Hydrate

A compound that contains water molecules within its structure.

Empirical Formula

A formula that shows the simplest whole-number ratio of the elements in a compound.

Oxoacid

An acid that contains hydrogen, oxygen, and another element.

Diatomic Molecule

A molecule composed of two atoms, which can be of the same or different elements.