Introductory Chemistry: Atomic Theory and Subatomic Particles

Vocabulary flashcards covering introductory atomic theory, historical development, subatomic particles, nuclear structure, isotope notation, and atomic mass calculations from Chapter 0 notes.

Four Elements

Early idea that all matter consists of earth, air, water, and fire, representing the early origins of Alchemy.

Atomists

Early thinkers contemporary to the "four elements" concept whose idea of "atomus" was not well received at the time.

Antoine Lavoisier

Chemist who established the "Law of Mass Conservation" in 1774.

Law of Mass Conservation

Fundamental theoretical concept formulated by Antoine Lavoisier in 1774.

Joseph Proust

Chemist who formulated the "Law of Definite Proportions" (fixed mass ratios) in 1794.

Law of Definite Proportions

Theoretical concept formulated by Joseph Proust in 1794 stating that compounds have fixed mass ratios.

John Dalton's Atomic Theory

Theory proposed in 1808 stating that matter consists of individual particles called atoms, all atoms of an element are the same, different elements have different atoms, atoms are indestructible, and compounds are made in whole number ratios.

Law of Multiple Proportions

Concept in John Dalton's Atomic Theory stating that compounds are made by combining atoms in whole number ratios that are fixed for a given compound.

Electron

Smallest sub-atomic particle with a negative charge ( $-1$ ), characterized by J. J. Thomson in 1897 and measured by Robert Millikan in 1909 as having an approximate mass of $9.08 \times 10^{-28}\,g$.

J. J. Thomson

Scientist who characterized the electron in 1897 as the smallest sub-atomic particle with a negative charge ( $-1$ ).

Robert Millikan

Scientist from U. of Chicago who conducted the "Oil drop experiment" in 1909 to measure the charge and mass (approx. $9.08 \times 10^{-28}\,g$) of the electron.

Oil Drop Experiment

1909 experiment carried out by Robert Millikan to measure the charge and mass of the electron.

Proton

Positively charged ( $+1$ ) sub-atomic particle larger than an electron, discovered and characterized in 1911 by E. Rutherford, with an approximate mass of $1.673 \times 10^{-24}\,g$.

E. Rutherford

Scientist who characterized the atomic nucleus and discovered the proton in 1911 via the "Gold Foil experiment" (with H. Geiger and E. Marsden), and co-"discovered" the neutron in 1932.

Gold Foil Experiment

1911 experiment carried out by E. Rutherford, H. Geiger, and E. Marsden that resulted in the characterization of the atomic nucleus.

Neutron

Sub-atomic particle with a neutral charge, "discovered" and characterized in 1932 by J. Chadwick and E. Rutherford, located in the nucleus with an approximate mass of $1.675 \times 10^{-24}\,g$.

J. Chadwick

Scientist who "discovered" and characterized the neutron alongside E. Rutherford in 1932.

Atomic Number (Z)

The number of protons in the nucleus of an atom, which is identical for each atom of a given element.

Mass Number

A counted number equal to the number of neutrons plus the atomic number ( $Z$ ) in the nucleus of an atom.

Isotopes

Atoms with the same atomic number but different mass numbers due to having the same proton count but different neutron counts.

Extended Symbol

Symbolic notation used to indicate an atom's specific isotopic identity, displaying the mass number, atomic number $Z$, and element Symbol (e.g., $^{14}_{6}\text{C}$).

(Relative) Atomic Mass

The weighted average mass of all atoms of an element calculated using the percent distribution of its naturally occurring isotopes, reported in Atomic Mass Units (amu).

Atomic Mass Unit (amu)

Unit used to report the mass of individual atoms, defined as $\frac{1}{12}$ the mass of a $^{12}_{6}\text{C}$ atom.