General Chemistry Chapter 11: Molecular Shapes, Valence Bond Theory, Molecular Orbital Theory

Molecular Geometry

3D-Shape that a molecule takes form of with its atoms when you cannot see electron groups.

VSEPR

Valence Electron Pair Repulsion

VSEPR Theory

Electron Groups are spaces of electron density around an atom (can be a lone or bonding pair).

Electron groups will always repel each other.

Electron groups take their positions around an atom so they minimize repulsion.

Electron Group Geometry

The shape that electrons and atoms make as if they were visible as atoms.

Linear Geometry

3 atoms bound together in a straight line shape

Trigonal Planar Geometry

2D triangle shape, 4 atoms bound together.

Tetrahedral Geometry

Triangular pyramid shape, 5 atoms bound together.

1 lone pair replacing an atom = trigonal pyramidal

2 lone pairs = bent shape

Trigonal Bipyramidal

a mirrored tetrahedral shape, 6 atoms.

1 lone pair = Seesaw

2 lone pairs = T-shape

3 lone pairs = Linear

Octahedral Shape

Mirrored square pyramid shape, 7 atoms

1 lone pair = square pyramidal

2 lone pairs = square planar

VSEPR Notation

A = central atom

X = number of bonded atoms

E = number of lone pair electrons (on the central atom)

Polar Molecule

Molecule with polar bonds that do not offset or cancel each other out.

(ex. a bent molecule with 2 polar bonds going in the direction of the center atom)

Valence Bond Theory

assumes that covalent bonds form when orbitals on different atoms overlap.

Sigma Bond

Covalent bond in which the orbital overlap is along the bond axis. End to end orbital overlap.

Pi Bond

Formed by mixing of orbitals that are not along the bonding axis in a molecule. Side by side overlap.

A double bond consists of 1 sigma and 1 pi bond.

A triple bond has 1 sigma and 2 pi bonds.

Hybridization

Mixing of orbitals to generate a new set of them for covalent bonding.

Electron Groups

Any bond pair or lone pair that is on any bonded atom.

Linear shape and 2 electron groups =

SP hybridization

Trigonal Planar and 3 electron groups =

SP² Hybridization

Tetrahedral and 4 groups =

SP³ Hybridization

Trigonal bipyramidal and 5 groups =

SP³D Hybridization

Octahedral and 6 groups =

SP³D² Hybridization