Forces of Attraction Lecture

Intramolecular forces Forces between atoms within a molecule 3 types: Ionic Cations and anions Covalent Positive nuclei and shared electrons Metallic Metal cations and mobile electrons Occurs in pure metals (Fe)

Intermolecular forces Forces between molecules Dispersion Dipolar Hydrogen bonds

Dispersion Weakest intermolecular force All molecules/compounds have this force between them Caused by temporary shifts of electrons in the electron cloud Only force between identical nonpolar molecules The more electrons an atom has the stronger the dispersion force F2 gas and Cl2 are gases at room temperature Br2= liquid and I2= solid

Dipolar Force between two polar molecules Caused by attraction between oppositely charged regions of the two polar molecules Example: HCl

Hydrogen bond Special dipolar attraction Attraction occurs between molecules containing H bonded to a small, electronegative atom (N, O or F only) with at least one lone pair of electrons