Chem 1110 Exam 2: Quantum Numbers, Chemical Bonding, Stoichiometry, and Molecular Geometry

Comprehensive vocabulary flashcards covering quantum numbers, electron configurations, stoichiometry, Lewis structures, resonance, VSEPR theory, and molecular geometries from Chem 1110.

Principal Quantum Number ($n$)

The quantum number that designates the principal electron shell or main energy level of an electron, taking positive integer values ($n = 1, 2, 3, \text{etc.}$).

Angular Momentum Quantum Number ($l$)

The quantum number that defines the shape of an orbital and its subshell ($s, p, d, f$), taking integer values from $0$ to $n - 1$.

Magnetic Quantum Number ($m_l$)

The quantum number that specifies the spatial orientation of an orbital within a subshell, taking integer values from $-l$ to $+l$.

Electron Spin Quantum Number ($m_s$)

The quantum number that indicates the intrinsic spin orientation of an electron in an orbital, which can only equal either $+\frac{1}{2}$ or $-\frac{1}{2}$.

Hund's Rule

The rule stating that when degenerate orbitals of equal energy are being filled, electrons occupy them singly with parallel spins before any pairing occurs.

Condensed Electron Configuration

A shorthand notation for representing electron configurations in which inner core electrons are replaced by the bracketed symbol of the preceding noble gas.

Core Electrons

The electrons in an atom that occupy completely filled inner principal energy levels and match the electron configuration of the preceding noble gas.

Valence Electrons

The electrons occupying the outermost principal energy level ($n$) of an atom that participate in chemical bonding and chemical reactions.

Anomalous Electron Configuration

A ground-state electron configuration that deviates from standard Aufbau ordering to achieve stability through half-filled or completely filled $d$ subshells, such as silver ($[Kr]5s^1 4d^{10}$) and copper.

Allotrope

Different structural forms of the same chemical element in the same physical state, such as elemental sulfur existing as eight-atom rings ($S_8$).

Law of Conservation of Mass

The fundamental principle stating that matter is neither created nor destroyed in a chemical reaction, meaning the total mass of reactants must equal the total mass of products.

Empirical Formula

The simplest chemical formula showing the lowest whole-number ratio of atoms of each element present in a compound, calculated from percent composition by mass.

Octet Rule

The chemical guideline stating that main-group atoms tend to gain, lose, or share electrons in bonding until surrounded by eight valence electrons, matching a stable noble gas configuration.

Expanded Octet

A molecular bonding situation where a central atom from Period 3 or beyond accommodates more than eight valence electrons (more than four electron pairs) by utilizing available $d$ orbitals.

Steric Number

The total number of electron-pair domains (bonded atoms plus nonbonding lone electron pairs) around the central atom of a molecule, determining its electron-pair geometry.

VSEPR Theory

Valence Shell Electron Pair Repulsion theory; a model predicting three-dimensional molecular geometry by minimizing electrostatic repulsion between valence electron pairs around a central atom.

Electron-Pair Geometry

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

Molecular Geometry

The three-dimensional spatial arrangement of only the bonded atoms in a molecule, defined relative to the central atom without including lone pairs in the shape name.

Nonpolar Covalent Bond

A covalent bond formed between two atoms with zero or negligible difference in electronegativity (such as $C-C$ or $H-P$), resulting in completely equal electron sharing.

Polar Covalent Bond

A covalent bond formed between atoms with differing electronegativities, resulting in unequal sharing of bonding electrons and partial electrostatic charges ($\delta^+$ and $\delta^-$).

Dipole Moment

A quantitative vector measure of net molecular polarity; symmetrical molecules like tetrahedral $CF_4$ have zero dipole moment because individual bond dipoles cancel out.

Resonance Structures

Two or more equally valid Lewis dot representations of a single molecule or ion having the same nuclear skeleton but different distributions of electrons.

Electron Repulsion Hierarchy

The relative order of repulsive forces between electron pairs in VSEPR theory: lone pair-lone pair repulsion > lone pair-bonding pair repulsion > bonding pair-bonding pair repulsion.

Bond Order

The number of electron pairs shared between a specific pair of bonded atoms (e.g., $1$ for a single bond, $2$ for a double bond, and $3$ for a triple bond).

Bond Length

The distance between the nuclei of two bonded atoms; for a given pair of atoms, higher bond order corresponds to shorter bond length and higher bond strength.

Electronegativity

A relative scale measuring the ability of an atom bonded in a molecule to attract shared electron density toward itself.

Ionic Bond Strength

The electrostatic attraction holding oppositely charged ions together, which increases with higher ion charges and shorter distances between ions (smaller ionic radii).

Free Radical

A chemical species or molecule possessing an odd number of valence electrons (such as $NO$ with $11$ or $IO$ with $13$), which cannot satisfy the octet rule on every atom.

Square Planar Molecular Geometry

A molecular shape characterized by a steric number of $6$ with four bonding pairs and two nonbonding lone pairs on the central atom (such as $KrF_4$ and $XeF_4$).

Trigonal Bipyramidal Geometry

The electron-pair geometry resulting from five electron domains surrounding a central atom, exhibiting axial and equatorial positions with bond angles of $90^\text{o}$, $120^\text{o}$, and $180^\text{o}$.