Electronic Structure and Periodic Properties of Elements

Vocabulary flashcards covering key terms from electromagnetic theory, quantum theory, atomic structure, and periodic properties.

Wave-particle duality

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

Speed of light (c)

The universal constant 3.00 x 10^8 m/s; relates wavelength and frequency via c = λν.

Wavelength (λ)

Distance between consecutive wave crests; measured in meters (m) or nanometers (nm).

Frequency (ν)

Number of wave cycles per second; units s^-1 or Hz.

Planck’s constant (h)

6.63 x 10^-34 J·s; relates photon energy to frequency: E = hν.

Photon

A quantum of light with energy E = hν.

Photon energy (E = hν)

Energy of a photon is proportional to its frequency.

Threshold frequency

Minimum frequency required to eject electrons in the photoelectric effect.

Photoelectric effect

Ejection of electrons from a metal surface when irradiated with light above threshold frequency; energy depends on frequency, not intensity.

De Broglie wavelength

Wavelength associated with a moving particle: λ = h/p.

Momentum (p) of a particle

Momentum of a non-relativistic particle is p = mv.

Bohr model

Electrons occupy discrete energy levels; transitions between levels emit/absorb photons.

Hydrogen energy levels

Energy of level n in hydrogen: E_n = -2.18×10^-18 J / n^2 (approx.).

Rydberg energy for hydrogen transitions

ΔE = -2.18×10^-18 J (1/nf^2 − 1/ni^2); energy difference between levels.

Atomic orbital

Three-dimensional region around the nucleus where electron probability is high; described by ψ^2.

Principal quantum number (n)

Determines orbital size and energy; n = 1, 2, 3, …; larger n → larger, higher-energy orbital.

Azimuthal/Angular momentum quantum number (l)

Describes orbital shape; l = 0,1,2,…, n−1; corresponds to s, p, d, f subshells.

Magnetic quantum number (m_l)

Describes orbital orientation in space; m_l ranges −l to +l.

Spin quantum number (m_s)

Describes electron spin; m_s = +1/2 or −1/2.

Aufbau principle

Electrons fill the lowest-energy subshells first before moving to higher energy subshells.

Pauli exclusion principle

No two electrons in an atom can have the exact same set of four quantum numbers.

Hund’s rule

For degenerate orbitals, the lowest-energy arrangement has the maximum number of unpaired electrons with parallel spins.

Degenerate orbitals

Orbitals within the same subshell that have the same energy.

Paramagnetic

Atoms with unpaired electrons; attracted to a magnetic field.

Diamagnetic

Atoms with all electrons paired; slightly repelled by a magnetic field.

Noble-gas core configuration

Abbreviated electron configuration using a noble gas core (e.g., [He] 2s2 2p4).

Core electrons

Electrons in inner shells that are not involved in bonding; shield the nucleus.

Valence electrons

Electrons in the outermost shell; determine chemical bonding and properties.

Electron configuration

Arrangement of electrons in atomic orbitals.

Isoelectronic

Species with the same electron configuration (e.g., N3-, O2-, F-, Ne, Na+, Mg2+).

Shielding

Electrons shield outer electrons from the full nuclear charge; inner electrons reduce effective attraction.

Effective Nuclear Charge (Z_eff)

Net positive charge experienced by a given electron after shielding; approximately Z_eff = Z − S.

Covalent radius

One-half the distance between nuclei of two identical covalently bonded atoms.

Ionic radius

Radius of an ion; cations are smaller than neutral atoms, anions larger due to electron repulsion.

Ionization energy (IE1)

Energy required to remove the first electron from a gaseous atom to form X+(g).

Ionization energy (IE2)

Energy required to remove the second electron from X+(g) to form X^2+(g).

IE trend

IE1 generally decreases down a group and increases across a period; IE2 > IE1.

Electron affinity (EA1)

Energy change when a gaseous atom gains an electron to form X−(g).

Second electron affinity (EA2)

Energy change for adding a second electron to X− to form X^{2−}.

Halogens and EA

Group 7A elements tend to have the most negative EA in a period.

Noble gas IE1

Noble gases have the highest first ionization energy in a period.

Isoelectronic trend (size)

In isoelectronic series, the more protons (higher Z) in the same electron configuration, the smaller the radius.