Valence Shell Electron Pair Repulsion (VSEPR) Theory

What is the real life 3D shape of molecules based on?

how many pairs of electrons are bonded and nonbonded on the central atom

Linear

(description of shape, BP, LP, Angle)

All atoms are in a straight line

• 2 or 4 bonded pairs

• 0 lone pairs

• Angle: 180

Trigonal Planar

(description of shape, BP, LP, Angle)

Atoms are in the same plane (flat) and make a triangle shape

• 3 bonded pairs

• 0 lone pairs

• Angle: 120

Tetrahedral

(description of shape, BP, LP, Angle)

Three atoms toward the bottom spread out like the legs of a tripod

• 4 bonded pairs

• 0 lone pairs

• Angle: 109.5

Triagonal Pyramidal

(description of shape, BP, LP, Angle)

The three attatched atoms make a triangle base of a pyramid with the central atom on top

• 3 bonded pairs

• 1 lone pair

• Angle: 107

Bent

(description of shape, BP, LP, Angle)

The three attatched atoms make a wide 7 or L shape

• 2 bonded pairs

• 2 lone pairs

• Angle: 104.5

Triagonal Bipyramidal

(description of shape, BP, LP, Angle)

The equatorial atoms make a flat triangle. The axial atoms go up and down

• 5 bonded pairs

• 0 lone pairs

• Angle:

  • E = 120

  • A = 90

Octahedral

(description of shape, BP, LP, Angle)

The equatorial atoms make a flat square. The axial atoms go up and down

• 6 bonded pairs

• 0 lone pairs

• Angle:

  • E = 90

  • A = 90

Square Pyramid

(description of shape, BP, LP, Angle)

Equatorial atoms make a flat square which is the base of the pyramid. Axial atom is the top

• 5 bonded pairs

• 1 lone pair

• Angle:

  • E = 90

  • A = 90

Square Planar

(description of shape, BP, LP, Angle)

The equatorial atoms make a flat square, The lone pairs are axial (straight up and down)

• 4 bonded pairs

• 2 lone pairs

• Angle: 90

T Shape

(description of shape, BP, LP, Angle)

All atoms make a T shape (flat)

• 3 bonded pairs

• 2 lone pairs

• Angle:

  • E = 185

  • A = 87.5

See Saw

(description of shape, BP, LP, Angle)

If this molecule rested on a surface, the lower atoms would be the base. The outer atoms could see saw their motion.

• 4 bonded pairs

• 1 lone pair

• Angle:

  • E = 154.5

  • A = 101.6

Lone pairs take up _____ space than a bonded pair

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