Quantum Mechanical Model – Topics from Chapters 5 & 6 (General Chemistry I) Vocabulary

Vocabulary flashcards covering key terms from the lecture notes on light, electrons, orbitals, and periodic trends.

Wavelength

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

Frequency

Number of wave cycles per unit time; units s⁻¹ (hertz, Hz).

Speed of Light (c)

Constant speed of electromagnetic waves in vacuum: 2.998 × 10^8 m/s.

Planck's Constant (h)

Constant relating energy of a photon to frequency: h = 6.626 × 10⁻³⁴ J·s.

Photon

Quantum of light; particle-like packet of energy with energy E = hν = hc/λ.

Energy of a Photon

Energy carried by a photon, given by E = hν = hc/λ.

Constructive Interference

Waves in phase combine to produce a brighter (larger amplitude) result.

Destructive Interference

Out-of-phase waves cancel, producing a dark or reduced-intensity result.

Diffraction

Bending of waves as they pass through openings or around obstacles.

Electromagnetic Spectrum

Range of all electromagnetic radiation ordered by energy, frequency, or wavelength.

Absorption Spectrum

Pattern showing wavelengths absorbed by a substance.

Emission Spectrum

Pattern showing wavelengths emitted by excited atoms or molecules.

Ground State

Lowest-energy state of an electron in an atom.

Excited State

Higher-energy state than the ground state.

Electron Transition

Movement of an electron between energy levels.

Photoelectric Effect

Ejection of electrons from a material upon light exposure; evidence of particle nature.

Wave-Particle Duality

Concept that particles (and light) exhibit both wave and particle properties.

de Broglie Wavelength

Relation λ = h/(mv); connects momentum to wavelength for a particle.

Heisenberg Uncertainty Principle

Δx Δp ≥ h/4π; fundamental limit to simultaneously knowing position and momentum.

Schrödinger Equation

Wave equation whose solutions give the probability density of finding an electron.

Probability Density

Probability of finding an electron in a given region, proportional to |ψ|².

Orbital

Region in space where there is a high probability of finding an electron; defined by quantum numbers.

Node

Location where the probability density (ψ²) is zero.

Principal Quantum Number (n)

Energy level of an electron; indicates distance from the nucleus; n = 1, 2, 3, …

Angular Momentum Quantum Number (l)

Sublevel type and orbital shape; l = 0,…,n−1 (s, p, d, f…).

Magnetic Quantum Number (ml)

Orientation of the orbital in space; ml ∈ −l,…,0,…,+l.

Spin Quantum Number (ms)

Direction of electron spin; ms = +½ or −½.

Aufbau Principle

Electrons fill orbitals from the lowest energy upward.

Pauli Exclusion Principle

No two electrons in an atom can have the same four quantum numbers; an orbital holds up to two electrons with opposite spins.

Hund's Rule

When filling degenerate orbitals, electrons enter unpaired into each orbital before pairing.

Valence Electrons

Electrons in the outermost energy level or in unfilled sublevels; involved in bonding.

Core Electrons

Electrons closer to the nucleus, not typically involved in bonding; shield inner electrons.

Isoelectronic

Having the same number of electrons as another species.

Ionic Charge

Positive or negative charge on an ion due to electron gain or loss.

Ionization Energy

Energy required to remove the outermost electron from a gaseous atom or ion.

Electron Affinity

Energy released when an electron is added to a gaseous atom or ion.

Coulomb's Law

Electrostatic force between charges is proportional to the product of charges and inversely proportional to the square of the distance (F ∝ q1q2/r²).

Effective Nuclear Charge (Zeff)

Net positive charge felt by a given electron; Zeff = Zactual − shielding.

Atomic Radius

Size of an atom; increases down a group and decreases across a period due to Zeff.

Noble Gas Shortcut

Electron configuration shorthand using [Noble Gas] core to represent filled inner shells.

Electron Configuration Notation

Notation showing the distribution of electrons among orbitals (e.g., 1s² 2s² 2p⁶).

Degenerate

Orbitals with the same energy level.

Paramagnetic

Material with at least one unpaired electron; attracted to a magnetic field.

Diamagnetic

Material with all electrons paired; repelled by a magnetic field.