Chem LO's exam 3

Gasses

low density, indefinite shape, indefinite volume, weak IM forces

Liquids

High density, indefinite shape, definite volume, moderate IM

Solids

High density, definite shape, definite volume, strong IM

Amorphous solids

Have no long range order

Crystalline solids

Have a long range order

Changing states of matter

Heating or cooling

Increasing pressure favors the more dense phase(gas to liquid)

Intermolecular forces

• Occur in between molecules

• Dispersion forces, dipole-dipole forces, hydrogen bonding, ion-dipole force

• The more present, the more higher the melting point

Intramolecular forces

Occur within molecules

Dispersion forces

• Occur between all molecules

• Caused by an instantaneous dipole creating an induced dipole

• Only IM force between non-polar molecules

• The greater the molar mass and surface area, the stronger the induced and instantaneous dipole

Dipole-dipole forces

• Occurs between 2 polar molecules with permanent dipoles

Hydrogen bonding

• Occurs when H is directly bonded with N, O, or F

• Strongest IM present in a pure substance

Ion-dipole forces

• Occurs in dissolved mixtures between polar molecules ad ions

• VERY STRONG

How to find boiling points

• Determine the IM forces in the molecule

• If 2 have the same, draw the LDS and the one with greater surface area has a higher boiling point

Valence Bond Theory

A localized electron model using s, p, d, and f orbitals like normal, but also including hybrid orbitals

• The geometry of overlapping orbitals determines molecular geometry

• Look at the number of atoms in the molecule and put it into sp³d^5 form

Hybridization

The process of combining standard s p d f atomic orbitals to create hybrid atomic orbitals

Guidelines for hybridization

1. Total number of atomic orbitals is conserved

2. Shapes and energies of hubrid orbitals are determined by particular combinations of standard atomic orbitals added together

3. The type of hybridization chosen has the lowest overall energy for the molecule

Sigma vs Pi bond

• Sigma=single

• Pi=poly(more than 1)

Molecular orbital