Arrangement of Electrons in Atoms

Comprehensive vocabulary flashcards covering the properties of light, quantum theory, atomic spectra, the Bohr and quantum mechanical models, quantum numbers, orbital geometries, and electron configuration rules.

Electromagnetic Radiation

A form of energy that exhibits wavelike behavior as it travels through space, characterized by wavelength and frequency.

Electromagnetic Spectrum

The continuum comprising all forms of radiation, of which visible light is the specific band detectable by human eyes.

Wavelength ($\lambda$)

The distance between corresponding points on adjacent waves, such as from crest to crest; visible light ranges from $400\,\text{nm}$ (blue) to $700\,\text{nm}$ (red).

Frequency ($\nu$)

The number of waves that pass a specified point per second, measured in cycles per second or hertz ($\text{Hz}$); visible light has a frequency of approximately $10^{14}\,\text{Hz}$.

Speed of Light ($c$)

The constant speed at which all electromagnetic radiation travels, mathematically expressed as $c = \lambda \cdot \nu = 3 \times 10^8\,\text{m/s}$.

Wave-Particle Duality

The principle that light and matter (such as electrons) can exhibit properties of both waves and particles.

Photoelectric Effect

The emission of electrons from a metal surface when light shines on it, occurring only when the light exceeds a specific threshold frequency.

Photon

A discrete particle of light or electromagnetic radiation that carries a specific quantum of energy.

Quantum

A discrete packet of energy carried by a photon, determined by the equation $E_{\text{photon}} = h\nu$.

Planck's Constant ($h$)

A fundamental physical constant with a value of $6.626 \times 10^{-34}\,\text{J}\cdot\text{s}$, relating a photon's energy to its frequency.

Continuous Spectrum

An uninterrupted band of colors representing all wavelengths of visible light within a range, formed when white light passes through a prism.

Line-Emission Spectrum

A spectrum consisting of narrow, distinct lines of color emitted by energized atoms; hydrogen displays 4 visible lines at $410\,\text{nm}$, $434\,\text{nm}$, $486\,\text{nm}$, and $657\,\text{nm}$.

Absorption Spectrum

A spectrum featuring dark lines where light of specific frequencies is absorbed when continuous radiation passes through a cool gas.

Bohr Model of the Atom

A 1913 atomic model proposing that electrons travel in quantized, discrete circular orbits like rungs of a ladder, where electrons cannot exist between energy levels.

Ground State

The lowest possible energy state of an atom or electron (e.g., $n = 1$ in hydrogen).

Excited State

A state in which an atom or electron has absorbed energy and moved to a higher potential energy level than its ground state.

Lyman Series

The series of ultraviolet emission lines produced when excited electrons drop down to the $n = 1$ energy level.

Balmer Series

The series of visible light emission lines produced when excited electrons drop down to the $n = 2$ energy level.

Paschen Series

The series of infrared emission lines produced when excited electrons drop down to the $n = 3$ energy level.

Louis de Broglie's Hypothesis

The proposal that electrons and other matter particles exhibit wave-like behavior and possess characteristic wavelengths.

Electron Diffraction

The bending and interference of electron beams as they pass through a thin metal foil, providing experimental proof that electrons have wavelengths.

Heisenberg Uncertainty Principle

A fundamental principle stating that it is impossible to determine simultaneously both the position and the velocity of an electron or any matter wave.

Quantum Mechanical Model

An atomic model based on Schrödinger's equations that uses mathematical probability to calculate three-dimensional, cloud-like orbital regions for electrons rather than fixed orbits.

Orbital

A three-dimensional cloud-like region around the nucleus where an electron is probably located, possessing uniform energy throughout the cloud.

Principal Quantum Number ($n$)

The quantum number that designates the main energy level occupied by the electron, with values $n = 1, 2, 3, 4\dots$.

Angular Momentum Quantum Number ($l$)

The quantum number that indicates the shape of an orbital, corresponding to the $s$, $p$, $d$, and $f$ sublevels.

Magnetic Quantum Number ($m$)

The quantum number indicating the spatial orientation and number of orbitals of a given shape ($s=1$, $p=3$, $d=5$, $f=7$).

Spin Quantum Number ($s$)

The quantum number that designates the two possible fundamental spin states for an electron in an orbital.

s Orbital

A spherically shaped orbital ($l = 0$) with only 1 possible spatial direction, where the electron has equal energy throughout the orbital.

p Orbital

A dumbbell-shaped orbital ($l = 1$) having 3 mutually perpendicular spatial directions ($p_x, p_y, p_z$), all possessing equal energy.

d Orbital

A cloverleaf-shaped orbital ($l = 2$) that exists in 5 distinct spatial orientations of equal energy.

f Orbital

A complex orbital ($l = 3$) having 7 distinct spatial orientations of equal energy.

Electron Configuration

The arrangement of electrons in an atom among available orbitals and sublevels, which explains elemental property trends.

Aufbau Principle

The rule (from the German for 'building up') stating that electrons occupy the lowest-energy sublevels first before filling higher energy levels (e.g., $4s$ fills before $3d$).

Pauli Exclusion Principle

The principle stating that no two electrons in an atom can have the same set of 4 quantum numbers; an orbital can hold a maximum of 2 electrons with opposite spins.

Hund's Rule

The rule stating that orbitals of equal energy are each occupied by one electron before any orbital is doubly occupied, and all singly occupied orbitals must have the same spin.

Orbital Notation

A visual representation using lines or boxes to depict orbitals and arrows to depict individual electrons and their spin orientations.

Electron-Configuration Notation

A written notation that represents electron sublevels with superscripts denoting the number of electrons present (e.g., $1s^2 2s^2 2p^6 3s^2 3p^1$).

Noble Gas Notation

An abbreviated electron configuration notation that uses the symbol of the previous noble gas enclosed in brackets to represent inner-shell core electrons, followed by the configuration of the outer energy level.