Section 2: Quantum Theory and Electronic Structure of Atoms - Vocabulary Flashcards

Vocabulary flashcards covering key terms from the lecture notes on quantum theory and atomic structure.

Quantum

A discrete unit of energy; Planck's idea that energy is emitted/absorbed in quanta.

Photon

A quantum of light energy with energy E = hν (or E = hc/λ).

Planck's constant (h)

Proportionality constant linking energy and frequency of a photon; used in E = hν.

Energy quantum (photon energy)

The energy carried by a photon; E = hν (or E = hc/λ).

Electromagnetic radiation

Radiation described by oscillating electric and magnetic fields, including visible light and X‑rays.

Electromagnetic spectrum

The full range of EM radiation ordered by frequency or wavelength.

Wavelength (λ)

Distance between successive crests of a wave; inversely related to frequency.

Frequency (ν)

Number of wave crests passing a point per second.

Speed of light (c)

Constant speed of light in vacuum: about 3.00 x 10^8 m/s.

Planck’s quantum theory

Energy is quantized; EM energy is emitted/absorbed in discrete quanta.

Black body radiation

Radiation emitted by a perfect absorber/ emitter; spectrum depends on temperature.

Hydrogen emission spectrum

Discrete light lines produced by electron transitions in hydrogen atoms.

Bohr model

Early atomic model with quantized orbits and energy-level transitions.

Rydberg constant (R_H)

Constant used in formulas for hydrogen spectral lines and energy levels.

Energy level (n)

Principal quantum number labeling discrete electron energies; n=1 is ground state.

Emission vs. absorption

Emission: electron drops to a lower energy level; absorption: electron moves to a higher level.

Prism

Optical device that disperses light into its component wavelengths.

Photon energy for a wavelength

Energy of a photon: E = hc/λ.

Atomic spectroscopy

Study of spectral lines to determine electronic structure and transitions.

Heisenberg Uncertainty Principle

Inability to know simultaneously exact position and momentum of a particle.

Schrödinger equation

Fundamental equation of quantum mechanics yielding the electron's wavefunction.

Wavefunction (ψ)

Mathematical function describing a system’s quantum state; |ψ|^2 gives probability density.

Orbital

Region around the nucleus with high probability of finding an electron; defined by quantum numbers.

Principal quantum number (n)

Quantum number that determines energy level and orbital size.

Azimuthal quantum number (l)

Defines orbital shape: s (l=0), p (l=1), d (l=2), f (l=3).

Magnetic quantum number (m_l)

Orientation of an orbital; values range from -l to +l.

Spin quantum number (m_s)

Electron spin: either +1/2 or -1/2.

Pauli Exclusion Principle

No two electrons in an atom can have the same four quantum numbers; max 2 electrons per orbital.

Hund's Rule

Electrons fill degenerate orbitals singly before pairing to maximize unpaired electrons.

Electron configuration

Distribution of electrons among available orbitals in an atom.

Aufbau principle

Electrons fill lowest-energy orbitals first to build up electron configurations.

Noble gas shorthand

Core electron configuration written with [Noble gas] followed by valence electrons.

Diamagnetic

Materials with all electrons paired; weakly repelled by magnetic fields.

Paramagnetic

Materials with unpaired electrons; attracted to magnetic fields.

Subshell (s, p, d, f)

Grouping of orbitals within a principal shell with capacity 2(2l+1) electrons.

Node

Region where electron probability is zero in an orbital; number of nodes increases with energy.

2s vs. 2p energy ordering

In many-electron atoms, 2s is typically lower in energy than 2p.

De Broglie wavelength

Matter waves have a wavelength λ = h/p, linking particle and wave properties.

Wave-particle duality

Idea that matter and light exhibit both wave-like and particle-like properties.

Orbital shapes (s, p, d, f)

s: spherical; p: dumbbell; d: cloverleaf; f: more complex shapes.

Transition energy (ΔE)

Energy change during an electron transition between levels; ΔE = hν.

Hydrogen energy level formula

En = -RH hc / n^2; energy of the electron in hydrogen.

Anomalous configurations (Cr, Cu)

Exceptions where real configurations differ from simple expectations for stability.

Electron spin magnetic quantum number

m_s value describing electron spin orientation (+1/2 or −1/2).