Light, Electrons, & the Periodic Table — Vocabulary

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

Light

A form of energy that is electromagnetic radiation; can behave as both a wave and a particle (photon).

Electromagnetic radiation

Energy that travels as waves of electric and magnetic fields; includes visible light and other wavelengths.

Wave

A disturbance that transfers energy through space; characterized by speed, amplitude, wavelength, and frequency.

c (speed of light)

The constant speed at which light travels in vacuum: 3.00 × 10^8 m/s.

Wavelength (λ)

Distance between successive crests (or troughs) of a wave.

Crest

Highest point of a wave.

Trough

Lowest point of a wave.

Amplitude

Height from the rest position to a crest or trough; measure of wave energy.

Frequency (ν)

Number of waves passing a point per second; unit is hertz (Hz).

Photon

A quantum of light with energy E = hν.

Planck's constant (h)

h = 6.626 × 10^-34 J·s; relates photon energy to frequency.

E = hν

Energy of a photon equals Planck's constant times its frequency.

ν = c/λ

Frequency equals the speed of light divided by wavelength.

Electromagnetic spectrum

All wavelengths of electromagnetic radiation arranged by frequency or wavelength.

Continuous spectrum

Light separated into a seamless range of colors when passed through a prism.

Visible spectrum

Portion of the EM spectrum visible to the human eye; roughly 400–700 nm.

Atomic emission spectrum

Distinct lines of light emitted by atoms, revealing the identity of the element.

Bohr model

Model with electrons in quantized, nucleus-centered orbits; energy increases with distance from the nucleus.

Quantum number (n)

Principal quantum number; indicates energy level or shell (n = 1, 2, 3, …).

Angular momentum quantum number (l)

Describes orbital shape; values 0 to n−1; subshells: s (0), p (1), d (2), f (3).

Subshell

Set of orbitals with the same n and l; designated by a letter (s, p, d, f).

Magnetic quantum number (ml)

Orientation of the orbital in space; values −l to +l; defines individual orbitals.

s orbital

Subshell with l = 0; spherical in shape.

p orbital

Subshell with l = 1; dumbbell-shaped; three orientations (px, py, pz).

d orbital

Subshell with l = 2; five shapes.

f orbital

Subshell with l = 3; seven shapes.

Aufbau principle

Electrons fill from the lowest energy to the highest; order s → p → d → f.

Hund's rule

Electrons occupy degenerate orbitals singly before pairing.

Pauli exclusion principle

No two electrons in an atom can have the same set of four quantum numbers; electrons in the same orbital have opposite spins.

Electron configuration

Arrangement of electrons in an atom's orbitals; ground state is the lowest-energy arrangement.

Orbital diagram

Graphical representation of electron configuration with arrows indicating spins.

Valence electrons

Electrons in the outermost energy shell that largely determine chemical behavior.

Core electrons

Electrons in inner shells that are not involved in bonding.

Noble gas configuration

Electron configuration that mirrors a noble gas; noble gases have full valence shells (8 valence electrons for most, 2 for He).

Abbreviated electron configuration

Short form using a noble gas core, e.g., [Ne] 3s^2 3p^5.

Ionization energy

Minimum energy required to remove an electron from a gaseous atom; endothermic; first ionization energy vs subsequent ionization energies.

Atomic size (radius)

Size of an atom; increases down a group, decreases across a period.

Metallic character

Tendency of elements to exhibit metallic properties; generally increases down a group and decreases across a period.

Nonmetallic character

Tendency of elements to exhibit nonmetal properties; generally increases across a period.

Blocks on the periodic table

s-block, p-block, d-block, f-block; correspond to which subshell is being filled.

Noble gases

Group 18 elements with full valence shells; highly inert (He is an exception with 2 electrons).

Valence vs. core

Valence electrons are in the outermost shell; core electrons are in inner shells.

Electron affinity

Energy change when an electron is added to a neutral atom; often releases energy but not always.

Ion charge

The charge on an ion formed when atoms lose or gain electrons to reach a noble-gas configuration.