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General Chemistry 1 > Unit 2: VSEPR Theory > Flashcards

Unit 2: VSEPR Theory Flashcards

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1
Q

What does VSEPR stand for?

A

Valence Shell Electron Pair Repulsion

Outer electrons

Electron pairs (bonding/nonbonding)

negatives repel (electrons are negative)

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2
Q

VSEPR Theory

A

Used to explain experiment

VSEPR references valence electrons

Explains spatial arrangement

Considers only central atom’s electrons

Doesn’t apply to 2 atom systems ( must be 3 or more)

Angle vs center atom

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3
Q

Steps to VSEPR Structures

A
  1. Write Lewis formula, ID central atom(s)
  2. Count electron pairs on center atom
  3. Apply VSEPR theory to determine electron

groups

  1. Apply VSEPR theory to determine bonding

arrangement

  1. Consider distortion from nonbonding
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4
Q

Electron Density Regions

2 types

A

Electron density regions repel

Lone pair – pair of electrons assigned completely to one atom in Lewis structures.

Bonding pair – pair of electrons shared between two atoms in Lewis structures.

Arrange to minimize

Build up one by one for multiple centers

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5
Q

Electronic vs Molecular Geometries

A

Electronic Geometry - Electron Configuration

Molecular Geometry - atom configuration

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6
Q

Electron Geometries

A
  • Based on Electron Density Regions

Lone pair = 1 electron density region

Bonding Pairs = 1 electron density region

so for instance a double bond would count as 1 not 2

Central atom determines the overall geometry

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7
Q

Electronic Geometry

of electron densities

also called electron groups

A

Standard Geometries

2 e- Densities → Linear → 180° between two atoms

3 e- Densities → Trigonal Planar → 120° between atoms

4 e- Densities → Tetrahedral → 109.5° between atoms

Octet Exceptions

5 e- Densities → Trigonal Bipyramidal → 90°, 120°, 180°

6 e- Densities → Octahedral → 90° & 180°

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8
Q

Molecular Geometries

Standard Compound

A

Standard Compound AxByUz

A= Central Atom

B= # bonded pairs

U = Unshared Pairs (lone pairs)

Repulsion:

U/U > U/B > BB

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9
Q

Molecular Geometry is based on?

Molecular Geometry considers ___

same or different than electronic geometry?

A

geometry based on angles

only considers atoms in the molecule

not always the same as electronic geometry

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10
Q

Electronic Geometry : Linear

What is its Molecular Geometry?

A

AB2

Two bonded, no unshared

Molecular Geometry: Linear

Forms 180°

generally Nonpolar

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11
Q

Electronic Geometry: Trigonal Planar

AB3

A

AB3

3 bonded, no unshared

Molecular Geometry: Trigonal Planar

forms 120°

Polarity depends upon the arrangement

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12
Q

Electronic Geometry: Trigonal Planar

AB2U

A

AB2U

2 bonded, 1 unshared

Molecular Geometry: Angular

Forms angles less than 120 degrees

Always Polar

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13
Q

Electronic Geometry: Tetrahedral

AB4

A

AB4

4 bonded, no unshared

Molecular Geometry: Tetrahedral

forms 109.5 degree angles

Polarity depends on arrangement

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14
Q

Electronic Geometry: Tetrahedral

AB3U

A

AB3U

3 bonded, 1 unshared

Molecular Geometry: Trigonal Pyramidal

forms about 107 degree angles

Polar

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15
Q

Electronic Geometry: Tetrahedral

AB2U2

A

AB2U2

2 bonded, 2 unshared

Molecular Geometry: Angular

Forms about 105 degree angles

Polar

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16
Q

Octet Exceptions

A

some instances where central atom defies octet rule

any elements that exist in period 3 or higher period have access to d subshell of that overall energy shell

d subshell contains 5 orbitals; gives access to a total of 18 valence electrons

allows bonds to make > 8 total electrons

17
Q

Electronic Geometry: Trigonal Bipyramidal

AB5

A

AB5

5 bonded, no unshared

Molecular Geometry: Trigonal Bipyramidal

Forms 90, 120, 180 degree angles

Polarity depends upon arrangement

18
Q

Electronic Geometry: Trigonal Bipyramidal

AB4U

A

AB4U

4 bonded pairs, 1 unshared pair

Molecular Geometry: See-saw

forms angles compressed from 90, 120, 180

Polar

19
Q

Electronic Geometry: Trigonal Bipyramidal

AB3U2

A

AB3U2

3 bonded, 2 unshared

Molecular Geometry: T Shaped

forms compressed 90 degree angles

Polar because of assymetry

20
Q

Electronic Geometry: Trigonal Bipyramidal

AB2U3

A

AB2U3

2 bonded, 3 unshared

Molecular Geometry: Linear

forms 180 degree

Polarity depends upon arrangement

21
Q

Electronic Geometry: Octahedral

AB6

A

AB6

6 bonded, no unshared

Molecular Geometry: Octahedral

froms 90, 180 degree angles

Polarity depends upon arrangement

22
Q

Electronic Geometry: Octahedral

AB5U

A

AB5U

5 bonded, no unshared

Moleculare Geometry: Square Pyramidal

forms 90, 180 degree angles

Polar

23
Q

Electronic Geometry: Octahedral

AB4U2

A

AB4U2

4 bonded, 2 unshared

Molecular Geometry: Square Planar

forms 90 & 180 degree angles

polarity depends upon arrangement

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General Chemistry 1 (18 decks)

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