Chemistry 103: Atomic Theory and Subatomic Structure

Vocabulary flashcards covering key concepts from lecture notes on atomic theory, subatomic particles, isotopes, and fundamental forces.

Atom

The smallest unit of an element.

Molecule

A group of two or more atoms held together by chemical bonds.

Compound

A substance formed when two or more different elements are chemically bonded together.

Isotopes

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

Atomic Number ($Z$)

The number of protons in an atom, which defines the chemical element.

Mass Number ($A$)

The total number of protons and neutrons in an atom ($A = \text{\# protons} + \text{\# neutrons}$).

Cathode-ray Tube

A glass tube consisting of two electrodes under very low pressure that emits cathode rays from the cathode ($-$) toward the anode ($+$) when high voltage is applied.

Plum Pudding Model

An atomic model proposed by J.J. Thomson depicting electrons embedded throughout a spherical cloud or blob of positive charge.

Nucleus

A tiny, dense, positively charged core at the center of an atom that holds almost all of its mass.

Alpha Particle

A small, positively charged particle consisting of two protons and two neutrons with a mass of approximately $4\,\text{amu}$.

Electrostatic Forces

Forces between static electric charges that act at a distance, are much stronger than gravitational forces, and can be both attractive or repulsive.

Gravitational Force

An always-attractive force between objects with mass, modeled by $F \propto \frac{M_1 M_2}{r^2}$.

Strong Nuclear Force

The strongest fundamental force that holds protons together in the nucleus over subatomic distances ($\sim 10^{-15}\,\text{m}$).

Weak Nuclear Force

A fundamental force occurring between elementary particles over extremely short distances ($\sim 10^{-18}\,\text{m}$) that is weaker than the electromagnetic or strong force.

Atomic Mass

The weighted average mass of an element's naturally occurring isotopes determined by the mass and relative abundance of each isotope.