Atomic Theory and Nuclear Chemistry Flashcards

Vocabulary flashcards covering atomic history, subatomic particles, isotopes, radioactive decay, half-life, and nuclear reactions from Unit 2.

Democritus

Ancient Greek philosopher (~400 B.C.) who proposed that matter is made up of tiny particles called atomos, or atoms.

John Dalton

Scientist who in 1803 supported the idea that matter is composed of extremely small, indivisible particles called atoms following numerous experiments.

J. J. Thompson

Scientist who identified the electron using cathode ray tubes in 1897.

Robert Millikan

Scientist who determined the charge of an electron using his oil drop apparatus in 1910.

Ernest Rutherford

Scientist who determined properties of the nucleus, including charge, with the gold foil experiment in 1911.

James Chadwick

Scientist who proved the existence of neutrons in 1932.

Atom

The smallest particle of an element that retains the properties of that element, with a radius of $5 \times 10^{-8}\,\text{mm}$.

Subatomic Particles Table

A reference table listing electrons ($e^-$, charge $-1$, relative mass $\frac{1}{1840}$), protons ($p^+$, charge $+1$, relative mass $1$), and neutrons ($n^0$, charge $0$, relative mass $1$).

Atomic number (Z)

The number of protons in an atom, which determines the identity of each element.

Atomic mass (A)

The total number of protons AND neutrons in an atom.

Atomic Mass Unit (amu)

A unit used to measure atomic mass, defined as $\frac{1}{12}$ the mass of Carbon-12.

Isotopes

Atoms which are the same element, but have different masses because they have different numbers of neutrons.

Band of Stability

A graph region containing all stable nuclei, where light stable nuclei ($Z < 20$) have a neutron-to-proton ratio $\frac{n}{p} = 1$ and heavy stable nuclei have $\frac{n}{p} = 1.5$.

Half-Life ($t_{1/2}$)

The constant amount of time it takes for half of a radioactive sample to decay, calculated using $A = A_0 \times \left(\frac{1}{2}\right)^{t / t_{1/2}}$.

Alpha Decay

A process where an unstable nucleus emits an alpha ($\alpha$) particle, which is a helium nucleus ($^4_2\text{He}$).

Beta Decay

A process where an unstable nucleus emits or captures a beta ($\beta$) particle, which is an electron ($^0_{-1}\beta^-$).

Gamma Decay

A process where an unstable nucleus emits a high-energy photon of light ($\gamma$), resulting in no change to protons or neutrons.

Positron

A positively-charged particle released during a specific type of radioactive decay.

Carbon Dating

A technique to determine the age of a fossil by measuring the percentage of remaining radioactive Carbon-14, which decays to Nitrogen-14 after death.

Nuclear Fusion

A nuclear process where small nuclei combine to release energy and form one larger nucleus, taking place in stars like the Sun.

Nuclear Fission

The splitting of a nucleus into smaller particles, which can produce a chain reaction and is used in nuclear power and nuclear weapons.

Control rods

Rods in a nuclear reactor that absorb excess neutrons to control the fission reaction and prevent an uncontrollable chain reaction.