Chemistry Unit 3 - Structure of the Atom Vocabulary

Vocabulary flashcards covering subatomic particles, atomic theory history, experiments, atomic numbers, mass numbers, isotope notations, and average atomic mass.

Proton

A subatomic particle located in the nucleus with a charge of +1 and a mass of about $1\,amu$.

Neutron

A subatomic particle located in the nucleus with a charge of 0 and a mass of about $1\,amu$.

Electron

A subatomic particle located in the electron cloud with a charge of -1 and a mass of almost $0\,amu$.

Democritus

The scientist who suggested tiny particles of matter using the idea of "atomos".

John Dalton

The scientist who proposed an atomic theory and created an early scientific atomic model proposing indivisible atoms.

J.J. Thomson

The scientist who used the cathode ray tube experiment to discover the electron.

Ernest Rutherford

The scientist who conducted the gold foil experiment and discovered the nucleus, concluding atoms are mostly empty space.

James Chadwick

The scientist who conducted nuclear particle experiments and discovered the neutron.

Niels Bohr

The scientist who created an atomic model showing electrons occupying energy levels around the nucleus.

Gold Foil Experiment

Rutherford's experiment in which particles were directed at thin gold foil, showing atoms are mostly empty space with a small, dense, positively charged nucleus.

Cathode Ray Experiment

Thomson's experiment using a cathode ray tube that revealed negatively charged particles known as electrons.

Atomic Number

A number that equals the number of protons in an atom, which identifies the element and equals the number of electrons in a neutral atom.

Mass Number

The total number of protons and neutrons in an atom, calculated as $\text{Mass Number} = \text{Protons} + \text{Neutrons}$.

Isotopes

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

Hyphen Notation

A method of writing an isotope using the element name followed by a hyphen and the mass number, such as Calcium-40.

Nuclear Notation

A method of writing an isotope where the mass number is written at the upper left of the element symbol and the atomic number at the lower left.

Average Atomic Mass

The weighted average mass of all naturally occurring isotopes of an element, calculated using $(\text{isotope mass} \times \text{decimal abundance}) + (\text{isotope mass} \times \text{decimal abundance}) + \dots$