VSEPR Theory - Molecular Geometry and Polarity

Vocabulary flashcards covering key terms, formula patterns, bond angles, and concepts of VSEPR theory and molecular polarity.

VSEPR Theory

Valence Shell Electron Pair Repulsion; a theory stating that electron groups around a central atom repel each other and arrange themselves as far apart as possible to determine molecular shape.

Electron Domain

Any region of electron density around a central atom, where a single, double, or triple bond, or a lone pair each counts as one single domain.

Bonding Pair

Electrons shared between atoms to form a chemical bond.

Lone Pair

Valence electrons on an atom not used in bonding, which occupy more space and repel more strongly than bonding pairs.

Central Atom

The atom in a molecule that is usually the least electronegative, with the exception of hydrogen.

Electron Geometry

The arrangement of all electron domains (both bonding domains and lone pairs) around the central atom.

Molecular Geometry

The spatial arrangement of bonded atoms only around the central atom, where lone pairs affect the overall shape but are omitted from the molecular name.

Linear Geometry ($AX_2$)

A molecular shape with $2$ electron domains and $0$ lone pairs on the central atom, producing a bond angle of $180^\times$ (e.g., $CO_2$).

Trigonal Planar Geometry ($AX_3$)

A molecular shape with $3$ electron domains and $0$ lone pairs on the central atom, spreading domains flat with a bond angle of $120^\times$ (e.g., $BF_3$).

Bent Geometry ($AX_2E$)

A molecular shape with $3$ electron domains ($2$ bonding pairs and $1$ lone pair) on the central atom, resulting in a bond angle of less than $120^\times$ (e.g., $SO_2$).

Tetrahedral Geometry ($AX_4$)

A three-dimensional molecular shape with $4$ electron domains and $0$ lone pairs on the central atom, featuring bond angles of $109.5^\times$ (e.g., $CH_4$).

Trigonal Pyramidal Geometry ($AX_3E$)

A molecular shape with $4$ electron domains ($3$ bonding pairs and $1$ lone pair) on the central atom, featuring a bond angle of about $107^\times$ (e.g., $NH_3$).

Bent Geometry ($AX_2E_2$)

A molecular shape with $4$ electron domains ($2$ bonding pairs and $2$ lone pairs) on the central atom, compressing the bond angle to about $104.5^\times$ (e.g., $H_2O$).

Expanded Octet Geometries

Molecular shapes for Period $3$ and heavier central atoms that can hold $5$ electron domains ($AX_5$, Trigonal Bipyramidal, e.g., $PCl_5$) or $6$ electron domains ($AX_6$, Octahedral, e.g., $SF_6$).

Molecular Polarity

The overall net dipole of a molecule, determined jointly by individual bond polarities (electronegativity differences) and molecular shape symmetry.