AP Chemistry: Atomic Structure, Bonding, and Spectroscopy

Comprehensive practice flashcards matching AP Chemistry Unit 1 topics: Atomic Structure, Periodic Trends, Photoelectron Spectroscopy, Chemical Bonding, Molecular Geometry (VSEPR), and Beer's Law.

Spectroscopy

The branch of science concerned with the investigation and measurement of wavelengths and energy (graphed as spectra) produced when matter interacts with or emits electromagnetic radiation.

Photon

A discrete particle or packet of electromagnetic radiation carrying energy proportional to its frequency according to $E = h\nu$.

Planck's Constant ($h$)

A fundamental physical constant equal to $6.626 \times 10^{-34}\,\text{J}\cdot\text{s}$ that relates the energy of a photon to its frequency.

Photoelectric Effect

The phenomenon in which light of sufficient frequency strikes a clean metal surface and ejects electrons, transferring photon energy to overcome the metal's attractive forces.

Work Function ($\phi$)

The minimum threshold energy required for an electron to overcome attractive forces and escape the surface of a specific metal during the photoelectric effect.

Microwave Spectroscopy

A spectroscopic method where the absorption of microwave radiation is associated with transitions between molecular rotational and torsional states.

Infrared (IR) Spectroscopy

A spectroscopic method where the absorption of infrared radiation corresponds to energetic transitions between molecular vibrational states (such as bond stretching).

Ultraviolet-Visible (UV-Vis) Spectroscopy

A spectroscopic technique where radiation corresponds to electronic energy level transitions, electronic excitations, or photoionizations in atoms and molecules.

Beer-Lambert Law

A law stating that the absorbance of light by a chemical species is directly proportional to its concentration and path length, expressed as $A = \varepsilon l c$.

Molar Absorptivity Constant ($\varepsilon$)

A characteristic constant in the Beer-Lambert Law describing how strongly a chemical species absorbs light at a given wavelength.

Covalent Bond

A chemical bond formed when valence electrons are shared between two atoms, typically occurring between nonmetals with low-to-middle electronegativity differences.

Ionic Bond

A chemical bond resulting from the complete transfer of valence electrons and the subsequent electrostatic attraction between oppositely charged ions, characterized by high electronegativity differences.

Metallic Bond

A bond characterized by a regular lattice of positive metal ions held together by a communal swarm of delocalized electrons that are free to move throughout the entire solid.

Lattice Energy

The energy released when gaseous cations and anions come together to form one mole of an ionic crystalline solid, directly dependent on ion charge magnitude and inversely dependent on interionic distance.

Substitutional Alloy

A metallic solid in which solute metal atoms replace host metal atoms within the crystal lattice, typically occurring between metals with atomic radii within approximately $15\%$ of each other.

Interstitial Alloy

An alloy formed when relatively small nonmetal atoms (such as carbon, hydrogen, boron, or nitrogen) occupy the spaces or holes between the larger metallic atoms in a crystal lattice.

Bond Length

The equilibrium internuclear distance between two bonded atoms corresponding to the minimum on a potential energy curve, where attractive and repulsive forces balance.

Bond Energy

The quantity of energy required to completely break one mole of a specific chemical bond between atoms in the gaseous state.

VSEPR Theory

Valence Shell Electron Pair Repulsion theory; a model used to predict molecular geometry based on the principle that electron pairs around a central atom repel each other and stay as far apart as possible.

Electron Pair Geometry (EPG)

The three-dimensional spatial arrangement of all electron-dense regions (both bonding pairs and lone pairs) surrounding a central atom.

Molecular Geometry (MG)

The spatial arrangement of the bonded nuclei around a central atom resulting from electron-electron repulsions.

Sigma ($\sigma$) Bond

A covalent bond formed by the direct head-on (end-to-end) overlap of atomic or hybridized orbitals along the internuclear axis.

Pi ($\pi$) Bond

A covalent bond formed by the sideways, parallel overlap of unhybridized p-orbitals in regions situated above and below the internuclear axis.

Orbital Hybridization

The mathematical mixing of non-equivalent atomic orbitals (such as s and p) on an atom to form degenerate hybrid orbitals of equivalent energy and orientation for chemical bonding.

Dipole Moment

A measure of the overall polarity of a molecule resulting from the vector addition of individual polar bond dipoles.

Formal Charge

The calculated charge assigned to an individual atom in a Lewis structure, equal to the atom's valence electrons minus the number of nonbonding electrons and half the number of bonding electrons.

Resonance Structures

Two or more valid Lewis representations for a molecule that possess identical nuclear arrangements but different allocations of delocalized electrons.

Aufbau Principle

The electron configuration rule stating that electrons fill available atomic orbitals of lowest energy first before occupying higher energy levels.

Pauli Exclusion Principle

A principle stating that each atomic orbital can hold a maximum of two electrons, and these two electrons must have opposite (antiparallel) spins.

Hund's Rule

The rule establishing that electrons occupying degenerate orbitals of equal energy spread out singly with parallel spins before pairing up.

Coulomb's Law

A principle stating that the electrostatic force and potential energy between charged particles are directly proportional to the product of charges ($q_1, q_2$) and inversely proportional to the distance ($r$) between them.

Effective Nuclear Charge ($Z_{\text{eff}}$)

The net attractive positive nuclear charge experienced by valence electrons, estimated by subtracting core shielding electrons ($S$) from total nuclear charge ($Z$): $Z_{\text{eff}} = Z - S$.

Electron Shielding

The repulsive effect exerted by inner core electrons on outer valence electrons, diminishing the electrostatic pull of the nuclear charge felt by the outer shell.

Photoelectron Spectroscopy (PES)

An analytical method that uses high-energy radiation to eject electrons from atoms, measuring their binding energies (peak position) and relative electron counts (peak height).

Ionization Energy

The energy required in $\text{kJ}\,\text{mol}^{-1}$ to remove an electron from a gaseous atom or ion in its ground state.

Electronegativity

A relative measure of the attraction an atom has for the shared pair of electrons within a chemical bond.

Atomic Radius

Half the distance between the nuclei of two identical bonded atoms, which decreases across a period due to increasing $Z_{\text{eff}}$ and increases down a group due to higher principal quantum numbers ($n$).