CHEM 1030 Exam 2 - Shapes, Angles & Hybridization

35 focused recall cards: VSEPR shapes and bond angles, electron-group to hybridization mapping, sigma/pi orbital patterns, oxygen bond orders and magnetism, and practice-exam molecule examples. No vocabulary or calculation drills. sp3d and sp3d2 are introductory course labels.

Steric number ($2, 3, 4, 5, 6$) to hybridization mapping

$2 \rightarrow sp$, $3 \rightarrow sp^2$, $4 \rightarrow sp^3$, $5 \rightarrow sp^3d$, $6 \rightarrow sp^3d^2$

$AX_2$ ($2$ bonding pairs, $0$ lone pairs): Geometries, angle, and hybridization

Electron geometry: linear; Molecular geometry: linear; Ideal angle: $180^\circ$; Hybridization: $sp$

$AX_3$ ($3$ bonding pairs, $0$ lone pairs): Geometries, angle, and hybridization

Electron geometry: trigonal planar; Molecular geometry: trigonal planar; Ideal angle: $120^\circ$; Hybridization: $sp^2$

$AX_2E_1$ ($2$ bonding pairs, $1$ lone pair): Geometries and bond angle

Electron geometry: trigonal planar; Molecular geometry: bent; Distorted angle: $< 120^\circ$

$AX_4$ ($4$ bonding pairs, $0$ lone pairs): Geometries, angle, and hybridization

Electron geometry: tetrahedral; Molecular geometry: tetrahedral; Ideal angle: $109.5^\circ$; Hybridization: $sp^3$

$AX_3E_1$ ($3$ bonding pairs, $1$ lone pair): Geometries and bond angle

Electron geometry: tetrahedral; Molecular geometry: trigonal pyramidal; Distorted angle: $< 109.5^\circ$

$AX_2E_2$ ($2$ bonding pairs, $2$ lone pairs): Geometries and bond angle

Electron geometry: tetrahedral; Molecular geometry: bent; Distorted angle: $< 109.5^\circ$

$AX_5$ ($5$ bonding pairs, $0$ lone pairs): Geometries, ideal angles, and hybridization

Electron geometry: trigonal bipyramidal; Molecular geometry: trigonal bipyramidal; Ideal angles: $90^\circ$, $120^\circ$, $180^\circ$; Hybridization: $sp^3d$

$AX_4E_1$ ($4$ bonding pairs, $1$ lone pair): Molecular geometry, lone pair location, and bond angles

Molecular geometry: seesaw; Lone pair position: equatorial; Distorted angles: $< 90^\circ$, $< 120^\circ$, $< 180^\circ$

$AX_3E_2$ ($3$ bonding pairs, $2$ lone pairs): Molecular geometry, lone pair locations, and bond angles

Molecular geometry: T-shaped; Lone pair positions: equatorial; Distorted angles: $< 90^\circ$, $< 180^\circ$

$AX_2E_3$ ($2$ bonding pairs, $3$ lone pairs): Molecular geometry, lone pair locations, and bond angle

Molecular geometry: linear; Lone pair positions: all $3$ equatorial; Angle: $180^\circ$

$AX_6$ ($6$ bonding pairs, $0$ lone pairs): Geometries, ideal angles, and hybridization

Electron geometry: octahedral; Molecular geometry: octahedral; Ideal angles: $90^\circ$, $180^\circ$; Hybridization: $sp^3d^2$

$AX_5E_1$ ($5$ bonding pairs, $1$ lone pair): Molecular geometry and bond angles

Molecular geometry: square pyramidal; Distorted angles: $< 90^\circ$, $< 180^\circ$

$AX_4E_2$ ($4$ bonding pairs, $2$ lone pairs): Molecular geometry, lone pair locations, and bond angles

Molecular geometry: square planar; Lone pair positions: opposite axial positions; Angles: $90^\circ$, $180^\circ$

Electron geometry vs. molecular geometry for $\text{H}_2\text{O}$

Electron geometry: tetrahedral ($4$ total electron pairs); Molecular geometry: bent (positions of atoms only)

Single bond: $\sigma$ and $\pi$ bond composition

$1\,\sigma$ bond, $0\,\pi$ bonds

Double bond: $\sigma$ and $\pi$ bond composition

$1\,\sigma$ bond, $1\,\pi$ bond

Triple bond: $\sigma$ and $\pi$ bond composition

$1\,\sigma$ bond, $2\,\pi$ bonds

Unhybridized $p$ orbitals remaining on central atom for $sp$, $sp^2$, and $sp^3$

$sp \rightarrow 2$ unhybridized $p$; $sp^2 \rightarrow 1$ unhybridized $p$; $sp^3 \rightarrow 0$ unhybridized $p$

Formaldehyde ($\text{H}_2\text{CO}$): Orbitals forming the $\text{C}=\text{O}$ $\sigma$ bond

End-to-end overlap of $\text{C}(sp^2)$ and $\text{O}(sp^2)$ hybrid orbitals

Formaldehyde ($\text{H}_2\text{CO}$): Orbitals forming the $\text{C}=\text{O}$ $\pi$ bond

Sideways overlap of parallel unhybridized $\text{C}(2p)$ and unhybridized $\text{O}(2p)$ orbitals

$\text{N}_2\text{O}$ (central $\text{N}$): Electron groups, molecular geometry, and polarity

$2$ electron groups; Linear molecular geometry; Polar (asymmetrical ends prevent dipole cancellation)

$\text{AsH}_3$: Electron geometry, molecular geometry, and bond angle

Electron geometry: tetrahedral ($3$ bonds, $1$ lone pair); Molecular geometry: trigonal pyramidal; Distorted angle: $< 109.5^\circ$

$\text{OF}_2$: Central oxygen hybridization, molecular geometry, and bond angle

Hybridization: $sp^3$ ($2$ bonds, $2$ lone pairs); Molecular geometry: bent; Distorted angle: $< 109.5^\circ$

$\text{SOCl}_2$: Central sulfur hybridization and molecular geometry

Hybridization: $sp^3$ ($3$ bonds, $1$ lone pair); Molecular geometry: trigonal pyramidal

$\text{NCO}^-$: Total valence electrons, central carbon hybridization, and molecular geometry

$16$ valence electrons; Hybridization: $sp$ ($2$ electron groups); Molecular geometry: linear

$\text{NCO}^-$ preferred resonance structure: Formal charges on $\text{N}$, $\text{C}$, and $\text{O}$

Structure with $\text{N}\equiv\text{C}-\text{O}^-$; Formal charges: $\text{N} = 0$, $\text{C} = 0$, $\text{O} = -1$

Valence MO energy ordering for $\text{O}_2$ and $\text{F}_2$ (low to high)

$$\sigma_{2s} < \sigma^*_{2s} < \sigma_{2p} < \pi_{2p} < \pi^*_{2p} < \sigma^*_{2p}$$

$\text{O}_2$: Valence electrons, MO bond order, and magnetism

$12$ valence electrons; Bond order: $2$; Paramagnetic ($2$ unpaired electrons in $\pi^*_{2p}$)

$\text{O}_2^+$: Valence electrons, MO bond order, and magnetism

$11$ valence electrons; Bond order: $2.5$; Paramagnetic ($1$ unpaired electron in $\pi^*_{2p}$)

$\text{O}_2^{2+}$: Valence electrons, MO bond order, and magnetism

$10$ valence electrons; Bond order: $3$; Diamagnetic ($0$ unpaired electrons)

$\text{O}_2^-$: Valence electrons, MO bond order, and magnetism

$13$ valence electrons; Bond order: $1.5$; Paramagnetic ($1$ unpaired electron in $\pi^*_{2p}$)

$\text{O}_2^{2-}$: Valence electrons, MO bond order, and magnetism

$14$ valence electrons; Bond order: $1$; Diamagnetic ($0$ unpaired electrons)

Oxygen species ($\text{O}_2^{2-}$, $\text{O}_2^-$, $\text{O}_2$, $\text{O}_2^+$, $\text{O}_2^{2+}$): Increasing bond order and bond length trend

Bond order: $\text{O}_2^{2-} (1) < \text{O}_2^- (1.5) < \text{O}_2 (2) < \text{O}_2^+ (2.5) < \text{O}_2^{2+} (3)$; Bond length decreases as bond order increases

Effect on bond order when adding vs. removing an electron from an antibonding ($\pi^*$) MO

Adding an antibonding electron decreases bond order by $0.5$; Removing an antibonding electron increases bond order by $0.5$