Atoms, Compounds, Molecules and Ions

Vocabulary flashcards covering key definitions, subatomic particle properties, atomic theories, laws, and atomic identifiers from Chapter 2.

Atomos

Meaning indivisible, it refers to the small, finite particles that the earliest Greek philosophers considered matter to be made of.

Dalton's Atomic Theory

A hypothesis proposed by John Dalton in 1807 stating that matter is composed of atoms, compounds consist of atoms of more than one element in constant relative numbers, and chemical reactions rearrange atoms without creating or destroying them.

Atom

The smallest unit of an element that can participate in a chemical change, possessing consistent size, mass, and chemical properties for a given element.

Compound

A substance composed of atoms of more than one element, in which the same types of atoms are always present in the same relative numbers.

Law of Conservation of Mass

The law stating that a chemical reaction rearranges atoms in chemical compounds without creating or destroying them.

Law of Definite Proportions

Proust's law stating that a pure compound always contains the same elements combined in the same mass proportions.

Subatomic Particles

The three primary particles that make up an atom, consisting of the proton, the neutron, and the electron.

Electron

A negatively charged subatomic particle with a charge of $-1.61 \times 10^{-19}\,\text{Coulombs}$ and a mass of $9.1 \times 10^{-28}\,\text{grams}$.

Proton

A positively charged subatomic particle located in the nucleus with a charge of $+1.61 \times 10^{-19}\,\text{Coulombs}$ and a mass of $1.67 \times 10^{-24}\,\text{g}$.

Nucleus

A small, dense, positively charged body located at the center of an atom that contains protons and neutrons.

Rutherford's Experiment

An experiment where gold foil was bombarded with alpha particles, revealing that an atom consists mostly of empty space with a small, dense, positively charged nucleus at its center.

Neutron

A neutral subatomic particle discovered by James Chadwick in 1932, located in the nucleus with no charge and a mass of approximately $1.67 \times 10^{-24}\,\text{g}$.

Atomic Number ($Z$)

Denoted by the letter $Z$, it is equal to the number of protons or the number of electrons in an atom, uniquely identifying an element.

Mass Number ($A$)

Denoted by the letter $A$, it is equal to the total number of protons plus neutrons present in the nucleus of an atom.

Isotopes

Atoms that have the same atomic number ($Z$), but differing mass numbers ($A$) due to a differing number of neutrons.