CEM 141 Chapter 1: Atomic Theory, Forces, and Intermolecular Interactions

Vocabulary flashcards covering core concepts from CEM 141 Chapter 1, including atomic models, subatomic discoveries, scientific arguments, fundamental forces, energy forms, and intermolecular interactions.

Atom

The basic building block of all matter, consisting of a positively charged nucleus with neutrons and positive protons, surrounded by a negatively charged electron cloud.

Element

A pure chemical substance consisting of atoms that all share the same number of protons, such as gold ($\text{Au}$) or oxygen gas ($\text{O}_2$).

Molecule

A chemical structure composed of two or more atoms held together by chemical bonds, which can consist of the same element (e.g., $\text{N}_2$) or different elements (e.g., $\text{H}_2\text{O}$).

Compound

A pure chemical substance made of two or more different elements that are chemically bonded together in a fixed ratio, such as table salt ($\text{NaCl}$) or carbon dioxide ($\text{CO}_2$).

Law of Conservation of Mass

A fundamental chemical principle formulated by Antoine Lavoisier stating that mass is neither created nor destroyed during a chemical reaction.

Law of Definite Proportions

A chemical law formulated by Joseph Proust stating that a given chemical compound always contains the same elements in the exact same mass ratios.

Law of Multiple Proportions

A principle formulated by John Dalton stating that when two elements form more than one compound, the masses of one element that combine with a fixed mass of the other are in small whole-number ratios.

Cathode Ray Experiment

An experiment performed by J.J. Thomson demonstrating that cathode rays deflect toward a positive electric plate, proving that atoms contain negatively charged subatomic particles called electrons.

Rutherford's Gold Foil Experiment

An experiment where alpha particles were fired at thin gold foil; over $99\%$ passed straight through while about $1\text{ in }20\text{,}000$ deflected by $45^\circ$ or more, proving the existence of a dense, positive nucleus.

Dalton's Atomic Model

An early 1800s atomic model proposing that matter is composed of tiny, indivisible spherical atoms that combine in fixed whole-number ratios.

Plum Pudding Model

J.J. Thomson's 1904 model proposing that an atom is a uniform sphere of positive charge with electrons embedded throughout like raisins in a pudding.

Rutherford's Nuclear Model

A 1911 atomic model proposing that an atom consists of a tiny, dense, positively charged nucleus containing nearly all the mass, surrounded mostly by empty space occupied by electrons.

Scientific Theory

A well-supported, evidence-based explanation for a broad set of observations or phenomena, constructed from repeated experiments, consistent data, and logical reasoning.

Claim

A statement or conclusion that answers a scientific question in a scientific argument.

Evidence

Data, measurements, observations, or experimental results that directly support or challenge a scientific claim.

Reasoning

The explanation that connects scientific evidence to a claim using established scientific principles, laws, or theories.

Gravitational Force

An attractive fundamental force between objects with mass that follows an inverse-square law; it is always attractive and extremely weak at the atomic level.

Electrostatic Force

The force between charged particles (such as protons and electrons) where opposite charges attract and like charges repel; it dominates atomic and chemical interactions.

Potential Energy

Stored energy dependent on particle position or arrangement; in chemistry, electrostatic attractions lower potential energy while repulsions increase it.

Kinetic Energy

The energy of motion; particles with higher kinetic energy move faster and collide more forcefully.

Total Energy

The sum of potential energy and kinetic energy in a system, which remains constant in an isolated system.

Equilibrium Bond Distance

The internuclear distance where attractive and repulsive electrostatic forces balance perfectly, corresponding to the minimum potential energy and highest stability of a two-atom system.

London Dispersion Forces (LDF)

Temporary intermolecular attractions arising when momentary shifts in electron density create fleeting dipoles that induce similar dipoles in nearby particles.

Polarizability

The ease with which an electron cloud of an atom or molecule can be distorted to form a temporary dipole.

Covalent Bond

A strong intramolecular chemical connection formed when two atoms share electrons, significantly lowering the potential energy of the system.