VSEPR Molecular Geometries Reference

Vocabulary flashcards covering VSEPR theory rules, steric numbers, bonding pairs, lone pairs, electron geometries, molecular geometries, and bond angles.

Steric Number (SN)

The sum calculated as $(\text{Bonding Pairs}) + (\text{Lone Pairs on Central Atom})$.

Repulsion Hierarchy (VSEPR)

The relative strength of electron pair repulsions: Lone Pair – Lone Pair > Lone Pair – Bonding Pair > Bonding Pair – Bonding Pair.

Angle Distortion

The phenomenon where non-bonding lone pairs exert greater electron repulsion, compressing bond angles below standard basic angles.

Linear (Steric Number 2)

Molecular geometry characterized by 2 bonding pairs, 0 lone pairs, linear electron geometry, and a bond angle of $180^\circ$.

Trigonal Planar (Steric Number 3, 0 Lone Pairs)

Molecular geometry characterized by 3 bonding pairs, 0 lone pairs, trigonal planar electron geometry, and a bond angle of $120^\circ$.

Bent or Angular (Steric Number 3)

Molecular geometry characterized by 2 bonding pairs, 1 lone pair, trigonal planar electron geometry, and a bond angle of $< 120^\circ$.

Tetrahedral (Steric Number 4, 0 Lone Pairs)

Molecular geometry characterized by 4 bonding pairs, 0 lone pairs, tetrahedral electron geometry, and a bond angle of $109.5^\circ$.

Trigonal Pyramid

Molecular geometry characterized by steric number 4 with 3 bonding pairs, 1 lone pair, tetrahedral electron geometry, and a bond angle of $< 109^\circ$.

Bent or Angular (Steric Number 4)

Molecular geometry characterized by 2 bonding pairs, 2 lone pairs, tetrahedral electron geometry, and a bond angle of $<< 109^\circ$.

Trigonal Bipyramid (Steric Number 5, 0 Lone Pairs)

Molecular geometry characterized by 5 bonding pairs, 0 lone pairs, trigonal bipyramid electron geometry, and bond angles of $90^\circ$ and $120^\circ$.

Sawhorse or Seesaw

Molecular geometry characterized by steric number 5 with 4 bonding pairs, 1 lone pair, trigonal bipyramid electron geometry, and bond angles of $< 90^\circ$ and $< 120^\circ$.

T-shape (Steric Number 5)

Molecular geometry characterized by 3 bonding pairs, 2 lone pairs, trigonal bipyramid electron geometry, and a bond angle of $< 90^\circ$.

Linear (Steric Number 5)

Molecular geometry characterized by 2 bonding pairs, 3 lone pairs, trigonal bipyramid electron geometry, and a bond angle of $180^\circ$.

Octahedral (Steric Number 6, 0 Lone Pairs)

Molecular geometry characterized by 6 bonding pairs, 0 lone pairs, octahedral electron geometry, and a bond angle of $90^\circ$.

Square Pyramid

Molecular geometry characterized by steric number 6 with 5 bonding pairs, 1 lone pair, octahedral electron geometry, and a bond angle of $< 90^\circ$.

Square Planar

Molecular geometry characterized by steric number 6 with 4 bonding pairs, 2 lone pairs, octahedral electron geometry, and a bond angle of $90^\circ$.

T-shape (Steric Number 6)

Molecular geometry characterized by 3 bonding pairs, 3 lone pairs, octahedral electron geometry, and a bond angle of $< 90^\circ$.

Linear (Steric Number 6)

Molecular geometry characterized by 2 bonding pairs, 4 lone pairs, octahedral electron geometry, and a bond angle of $180^\circ$.