3.2 Explaining Molecular Formulas

diatomic elements

“I H ave N o Br ight O r Cl ever F riends” (ex. H2)

molecular compounds

covalent bonds between NM + NM; DOES NOT conduct electricity; can be solid liquid or gas

empirical formula

simplest whole number rations of atoms in compound; not useful for molecular but for ionic

molecular formula

shows the actual number of atoms that are covalently bonded

lewis formula

using lewis symbols to show electron sharing in covalent bonds

structural formila

structural design

stereochemical formula

3d shape structure. ex. tetrahedral

VSEPR theory

Valence Shell Electron Pair Repulsion; the theory behind molecular shapes

polar molecules

one end slightly negative and one end slightly positive

0\.0-0.4 EN difference

covalent; NON POLAR (pure covalent)

0\.5-1.0 EN difference

covalent; SLIGHTLY POLAR

1\.1 - 2.0 EN difference

covalent; VERY POLAR

2\.1-4.0 EN difference

ionic

bond dipole (dipole moment)

a measure of the polarity of a chemical bond between 2 atoms in a molecule

dipole moment

represented by an arrow that points from LOW to HIGH electronegativity, showing the direction of the electrons

non polar molecules

the bond dipoles cancel out leaving a molecular dipole of 0; symmetrical molecules Ex. CO2, CH4

polar molecules

the bond dipoles do not cancel out leaving a non-zero net molecular dipole (one side slightly more electronegative) ex. H2O, HCl, NH3, ClCH