Atomic Theory and Nuclear Chemistry

Comprehensive vocabulary flashcards covering atomic structure, historical atomic models, isotopes, and types of nuclear radiation.

Atom

The smallest unit of an element.

Proton

A positively charged ($+$) subatomic particle located in the nucleus.

Neutron

A neutral ($0$) subatomic particle located in the nucleus.

Electron

A negatively charged ($-$) subatomic particle that moves around the nucleus.

Nucleus

The dense central region of an atom that contains most of the atom's mass.

Orbitals

The regions around the nucleus where electrons move.

Democritus

A Greek philosopher who studied matter and proposed that it is made of tiny, solid, indivisible particles.

Atom (Etymology)

A term derived from Greek meaning indivisible.

Dalton's Atomic Theory

A theory stating that matter is made of atoms, atoms of the same element are alike, and atoms combine to form compounds; it helped develop modern atomic theory.

Element

A substance composed of only one type of atom.

Compound

A substance formed from two or more elements chemically combined.

Cathode Ray Tube

The experimental apparatus used by Thomson to discover the electron.

Plum Pudding Model

Thomson's atomic model featuring negative electrons positioned inside a positive sphere, lacking a nucleus.

Gold Foil Experiment

An experiment conducted by Rutherford where particles were directed at a thin sheet of gold, leading to the discovery of the nucleus.

Rutherford's Atomic Model

An atomic model concluding that the atom is mostly empty space with a small, positive nucleus.

Energy Levels

Specific regions in an atom where electrons have defined energies.

Bohr's Atomic Model

An atomic model proposing that electrons occupy specific energy levels and release or absorb photons when changing levels.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons (e.g., Potassium-$39$ and Potassium-$40$).

Mass Number

The sum of protons and neutrons in an atom: $\text{Mass number} = \text{Protons} + \text{Neutrons}$.

Natural Abundance

The percentage of each isotope found in nature; it remains constant for each element and is used to calculate atomic mass.

Radioactivity

The release of radiation from an unstable nucleus.

Radiation

Energy or particles released by a source.

Chemical Reaction (vs. Nuclear Reaction)

A process involving changes in electrons and chemical bonds, while the nucleus remains unaffected.

Nuclear Reaction (vs. Chemical Reaction)

A process in which the nucleus of an atom undergoes changes.

Nuclear Stability

A state achieved in a nucleus by maintaining a suitable balance between protons and neutrons.

Alpha Radiation ($\alpha$)

Radiation composed of $2$ protons and $2$ neutrons with a charge of $+2$ and low penetration power (stopped by paper).

Beta Radiation ($\beta$)

Radiation composed of a fast-moving electron in beta-minus decay with a charge of $-1$ and medium penetration power (can be stopped by thin aluminum).

Gamma Radiation ($\gamma$)

High-penetration energy radiation with no mass and a charge of $0$ that releases excess nuclear energy and requires thick lead or concrete for significant shielding.