CHEM 103 Unit 1: Atomic Theory

Vocabulary practice flashcards covering fundamental chemistry laws, historical atomic models, light & electromagnetic spectrum properties, quantum mechanics, electron configurations, and periodic trends from CHEM 103 Unit 1.

Substance

A form of matter that has a definite composition and distinct physical and chemical properties.

Law of Conservation of Mass

A foundational chemistry law formulated by A. Lavoisier stating that matter is neither created nor destroyed during a chemical reaction.

Law of Definite Proportions

A law formulated by J. Proust stating that all samples of a given compound have the same proportions of their constituent elements by mass.

Law of Multiple Proportions

A law formulated by J. Dalton stating that when two elements form two different compounds, the masses of one element combining with $1\,g$ of the other express a ratio of small, whole numbers.

Plum Pudding Model

An early atomic model proposed by J.J. Thomson in 1904 depicting negatively charged electrons embedded within a sphere of uniform positive charge.

Isotopes

Atoms of the same element containing the same number of protons but different numbers of neutrons, giving them distinct atomic masses.

Cation

A positively charged ion formed when a neutral atom or molecule loses one or more electrons.

Anion

A negatively charged ion formed when a neutral atom or molecule gains one or more electrons.

Wavelength ($\lambda$)

The linear distance between two consecutive peaks or troughs in an electromagnetic wave.

Frequency ($\nu$)

The number of wave cycles that pass a given point in space per second, measured in hertz ($\text{Hz}$) or $\text{s}^{-1}$.

Amplitude

The height of a wave crest or depth of a trough relative to the zero-level line.

Refraction

The bending of a light wave's path when passing from one medium to another due to an instantaneous change in speed.

Diffraction

The bending of light or matter waves around the edges of an obstacle or through a narrow opening.

Blackbody

An idealized physical body that absorbs all incoming light and emits radiation whose frequency spectrum depends solely on temperature.

Photoelectric Effect

The emission of electrons from a metal surface when irradiated with light above a specific threshold frequency.

Work Function

The minimum energy required to eject an electron from the surface of a specific metal or alloy.

Ground State

The lowest possible electronic energy level of an atom or ion ($n = 1$ for hydrogen).

Excited State

Any electronic state of an atom or ion having higher potential energy than its ground state ($n > 1$).

de Broglie Wavelength

The wavelength associated with a moving particle, defined by the relation $\lambda = \frac{h}{p}$.

Heisenberg Uncertainty Principle

A fundamental rule stating that it is impossible to simultaneously measure the exact position and momentum of a subatomic particle ($\Delta p \Delta x \ge \frac{h}{4\pi}$).

Wavefunction ($\psi$)

A mathematical solution to the Schrödinger equation describing an electron in three dimensions, whose square ($\psi^2$) represents probability density.

Principal Quantum Number ($n$)

The quantum number determining an atomic orbital's overall energy level and size ($n = 1, 2, 3, \dots$).

Angular Momentum Quantum Number ($\ell$)

The quantum number defining the three-dimensional shape of an orbital subshell, ranging from $\ell = 0$ to $\ell = n - 1$.

Magnetic Quantum Number ($m_\ell$)

The quantum number specifying the 3D orientation of an orbital in space, ranging from $m_\ell = -\ell$ to $m_\ell = +\ell$.

Spin Quantum Number ($m_s$)

The quantum number specifying the intrinsic spin axis of an electron, taking allowed values of $+\frac{1}{2}$ or $-\frac{1}{2}$.

Stern-Gerlach Experiment

An experiment demonstrating electron spin quantization by splitting a beam of silver atoms in an inhomogeneous magnetic field.

Aufbau Principle

The rule for constructing electron configurations where electrons systematically fill available lower-energy orbitals before occupying higher-energy ones.

Pauli Exclusion Principle

The quantum mechanical requirement stating that no two electrons in an atom can share the exact same set of four quantum numbers.

Hund's Rule

The principle stating that degenerate orbitals of equal energy are each occupied by one electron with parallel spin before pairing occurs.

Effective Nuclear Charge ($Z_{\text{eff}}$)

The net positive nuclear attraction felt by an electron, approximated as $Z_{\text{eff}} = Z - S$ where $S$ represents core shielding.

Penetration

The degree to which an electron orbital extends close to the nucleus through inner shells, lowering the electron's energy and increasing stability.

Paramagnetic

The magnetic condition of an atom, ion, or compound possessing one or more unpaired electrons, causing attraction to an external magnetic field.

Diamagnetic

The magnetic condition of a species having all electrons paired, resulting in weak repulsion by a magnetic field.

Ionization Energy (IE)

The quantity of energy required to remove an electron completely from a neutral gaseous atom or ion in its ground state.

Electron Affinity (EA)

The energy change associated with adding an electron to an isolated neutral atom in the gas phase.

Oxidizing Agent

A substance in a redox reaction that accepts electrons, causing another species to be oxidized while itself being reduced.

Reducing Agent

A substance in a redox reaction that donates electrons, causing another species to be reduced while itself being oxidized.

Basic Oxide

A metal oxide that reacts with water to generate hydroxide ions and form an alkaline solution.

Acidic Oxide

A nonmetal oxide that reacts with water to form an acidic solution.