Chapter 12 Honors Chem - States of Matter

metallic bonds

form between atoms of the same metallic element or between combinations of metals

ionic compounds

form the transfer of electrons between metal and nonmetal atoms.

covalent bonds

form between atoms that share electrons as nonmetals

intramolecular forces

chemical bonds; forces of attraction directly between atoms and ions

intermolecular forces

forces of attraction that cause entire molecules to be attracted to other molecules or particles

3 main classifications of intermolecular forces

London dispersion forces, dipole-dipole forces, and hydrogen bonds

London dispersion forces

caused by electrons temporarily moving to one side of the electron cloud of the atom or molecule

weakest type of intermolecular force

London dispersion forces

intermolecular force all substances possess

London dispersion forces

only intermolecular force for monatomic gases and nonpolar substances

London dispersion forces

dipole-dipole forces

stronger intermolecular forces that exist between two or more molecules that have permanent dipoles. The partially positive side of one molecule is attracted to the partially negative side of the other molecule.

hydrogen bonds

a special type of dipole-dipole force. Hydrogen atoms are so small that they cause electron density to migrate heavily to very electronegative atoms (nitrogen, oxygen, and fluorine) within a covalent bond.

intermolecular forces

can be disrupted during physical change.

strength of intermolecular forces

Hydrogen bonding is a stronger intermolecular force than dipole-dipole

forces. Both types of intermolecular forces are stronger than London dispersion forces. Dispersion forces are always present but are ignored if hydrogen bonding or dipole-dipole forces are present.

intermolecular forces and melting/boiling points

Compounds with stronger intermolecular forces have higher melting/boiling points. This is because it takes more energy to disrupt stronger attractions between molecules. However, If an atom or molecule is large enough, it might have enough dispersion forces that make its melting/boiling point larger than a smaller molecule with dipole-dipole forces or hydrogen bonding.

large electron clouds

For atoms and molecules that only have dispersion forces, larger electron clouds are more polarizable. Therefore, particles with larger electron clouds typically have higher melting/boiling points.