SCH4U - Chemistry 12 (2024-25) - A

Summary

• Intermolecular forces are the attractive forces between molecules that cause them to interact
• Dipole-dipole forces occur between polar molecules where opposite poles are attracted to each other and molecules arrange themselves in such a way as to maximize this attraction
• Hydrogen bonding is a special type of intermolecular force that occurs in molecules that have a hydrogen atom bound to an oxygen, nitrogen or fluorine atom
• Hydrogen bonding is similar to dipole-dipole forces but the bond is stronger
• Hydrogen bonding gives water many of its unique qualities
• London dispersion forces occur when temporary dipoles form in non-polar molecules
• Temporary dipoles are caused by the random distribution of electrons around the nucleus, when electrons become disproportionately distributed, temporary +ve and -ve poles form which can then induce temporary poles in neighbouring molecules
• Intermolecular forces impact many physical characteristics such as boiling point and melting point.  For example, stronger intermolecular forces cause higher melting and boiling points
• The properties of solids are directly related to their structural characteristics
• Ionic crystals are held together by ionic bonds and tend to have high melting points, brittle texture and have hard surfaces
• Metallic crystals are structurally represented as a sea of electrons surrounding the nuclei of metallic atoms
• Metallic crystals tend to be flexible, good electrical conductors and have shiny surfaces
• Molecular crystals are held together by intermolecular forces and tend to have low melting points, are soft and do not conduct electricity well
• Covalent network crystals are connected entirely by covalent bonds, they tend to be very hard, have high melting points and do not conduct electricity well