Electronic Structure & Light – Key Vocabulary

A comprehensive set of vocabulary flashcards covering light properties, quantum theory, atomic models, quantum numbers, and electron configurations, derived from the Electronic Structure lecture notes.

Frequency (ν)

Number of wavelengths that pass a given point per second, measured in s⁻¹ (Hertz).

Wavelength (λ)

Distance from peak-to-peak (or trough-to-trough) of a wave, usually expressed in meters or related units (nm, cm).

Amplitude

Height of a crest or depth of a trough, indicating wave intensity.

Speed of light (c)

Constant velocity at which light travels in a vacuum, 3.00 × 10⁸ m s⁻¹.

Electromagnetic Radiation (EMR)

Form of energy with electric and magnetic fields that can travel through a vacuum; also called light.

Electromagnetic Spectrum

Complete range of EMR types, ordered by wavelength and frequency.

Photon

Quantized “packet” of light energy; energy equals hν.

Planck’s Constant (h)

Proportionality constant relating photon energy and frequency; 6.626 × 10⁻³⁴ J·s.

Emission Spectrum

Set of discrete wavelengths emitted by excited atoms when electrons return to lower energy levels.

Excitation

Process in which an electron absorbs energy and moves to a higher energy level.

Bohr Model

Atomic model with electrons in fixed circular orbits; explains hydrogen line spectrum.

Ground State

Lowest energy level an electron can occupy in an atom.

Excited State

Energy level higher than the ground state occupied after absorption of energy.

Principal Quantum Number (n)

Quantum number indicating relative energy and size of an orbital; integral values 1,2,3…

Angular Momentum Quantum Number (ℓ)

Quantum number defining sublevel shape; integral values 0 to n–1 (s,p,d,f…).

Magnetic Quantum Number (mℓ)

Quantum number describing orbital orientation; integral values –ℓ to +ℓ.

Electron Spin Quantum Number (ms)

Quantum number indicating electron spin direction; +½ or –½.

Orbital

Three-dimensional probability region where an electron is likely to be found.

s Sublevel

Sublevel with ℓ = 0; one spherical orbital, holds maximum 2 electrons.

p Sublevel

Sublevel with ℓ = 1; three dumbbell orbitals, holds maximum 6 electrons.

d Sublevel

Sublevel with ℓ = 2; five orbitals, holds maximum 10 electrons.

f Sublevel

Sublevel with ℓ = 3; seven complex orbitals, holds maximum 14 electrons.

Pauli Exclusion Principle

No two electrons in the same atom can have identical set of four quantum numbers; max two electrons per orbital with opposite spins.

Hund’s Rule

Electrons occupy degenerate orbitals singly with parallel spins before pairing up.

Electron Configuration

Notation showing distribution of electrons among orbitals of an atom in order of increasing energy.

Aufbau Principle

Electrons fill lowest-energy orbitals first before higher ones.

Noble-Gas Configuration

Abbreviated electron configuration using the symbol of the preceding noble gas in brackets plus remaining electrons.

Valence Electrons

Electrons in the outermost principal energy level; determine chemical properties.

Core Electrons

Electrons in inner shells, not involved in most chemical reactions.

Transition Elements

d-block metals whose valence includes ns and (n–1)d electrons.

Flame Test

Analytical method using characteristic colors from electron transitions to identify elements.

Frequency–Wavelength Relationship

c = λν; frequency is inversely proportional to wavelength for light.

Photon Energy Equation

E = hν, relating energy of a photon to its frequency.

Quantum Mechanical Model

Modern atomic model using wave functions (ψ) to describe electron probability distributions.

Hamiltonian (ℋ)

Operator in Schrödinger equation combining kinetic and potential energy of electrons.

Wave Function (ψ)

Mathematical description of an electron’s matter-wave; |ψ|² gives probability density.

Probability Density

Value of ψ² indicating likelihood of finding an electron at a point in space.

Principal Energy Level

Set of orbitals with the same principal quantum number n.

Sublevel (Subshell)

Group of orbitals with the same n and ℓ values.

Degenerate Orbitals

Orbitals within the same sublevel that have equal energy.

Emission (Radiative Transition)

Release of energy as a photon when an electron drops to a lower energy level.

Absorption

Uptake of energy causing an electron to move to a higher energy level.

Representative Elements

s- and p-block elements whose group number equals number of valence electrons.

Periodic Table Blocks

Sections (s, p, d, f) corresponding to the sublevel being filled with electrons.

Group Number

Vertical column identifier; for A-groups indicates valence electron count.

Period Number

Horizontal row identifier corresponding to highest occupied principal energy level.

Amplitude–Intensity Relationship

Greater amplitude indicates higher wave energy/intensity.

Long Wavelength

Wave property associated with low frequency and low energy.

Short Wavelength

Wave property associated with high frequency and high energy.