VSEPR theory Bond Polarity Intermolecular Forces Nomenclature 8.1,8.2, 8.3, 8.4 and 9.3 VSEPR theory Bond Polarity Intermolecular Forces Nomenclature

Review of Molecular compounds covalent bonding (video) Molecular (covalent) compounds share e-. Recognize by NM/NM ex: PCl3 Diatomic Elements are covalent (scared 7) H2, N2, O2, F2, Cl2, Br2, I2 Biological mc (mc=molecule) are covalent

Octet Rule/Lewis Dot structures Octet Rule: all molecular compounds share e- so each element obtains a noble gas config. (8e-) Lewis Dot Structure (LDS): visual representation of covalent bonds showing the octet rule. Each element has 8 dots (except H)

Rules for LDS All atoms have octet (except H- only 2) Usually have 1 center atom (the others come off of it)(C loves to be the center of attention) Cannot add/subtract electrons for fun Try for symmetry. Single bonds (2 e-), double bonds (4 e-) triple bonds (6 e-)

LDS example Lewis Dot structures (video) 1 Carbon 2 Fluorine Combine To form CF4

VSEPR THEORY Valence Shell Electron Pair Repulsion Theory Pairs of e- will push away from each other to be as far apart as possible This creates shapes Tetrahedral, pyramidal, bent

Bond Polarity Nonpolar Bond: electrons are evenly shared between atoms. Polar Bond: electrons are shared unevenly between atoms creating a slightly +/- situation

How do you tell if a bond is P or NP? Polarity (video) Subtract electronegativites of atoms and if difference is: Do not memorize e-neg (pg. 177) Greater than 1.5 Ionic Less than .5 Nonpolar (NP) Greater than .5 Polar Example: water (H and O): 3.5 -2.1 = 1.4 P Example: methane (C and H) 2.5 – 2.1 = .4 NP

Intermolecular Forces (IMF) Molecular Compounds Ionic Compouds IMF: attraction between mc Strength of IMF depends on polarity Have no IMF, all equally attracted to each other Very strong

3 types of IMF Van der Waals or Dispersion: weak attraction between NP mc – electrons are just kind of shared bt mc Dipole-Dipole: attraction between Polar mc – act like a weak magnet (semi +/- attractions) Hydrogen Bonding: fairly strong attraction between mc that are polar and have H in it. (stronger +/- attraction)

Dispersion Forces

Dipole-dipole interactions

Hydrogen Bonding

Naming Molecular Compounds Because molecules can have such varying formulas (ex: CO and CO2), naming is different from Ionic. When naming you must say how many of each atom you have 1-mono, 2-di, 3-tri, 4-tetra, 5-penta, 6-hexa, 7-hepta, 8-octa, 9-nano, 10-deca CO2 – carbon dioxide Mono is optional for first atom

Molecular Nomenclature Writing Molecular Names Writing Molecular Formulas Write element name Second element ends in -ide Subscripts become Prefixes 1-mono, 2-di, 3-tri, 4-tetra, 5-penta, 6-hexa, 7-hepta, 8-octa, 9-nano, 10-deca Example: N2O7 Dinitrogen Heptaoxide Write symbols of elements in compound Prefixes become subscripts Ex: Tricarbon tetraphosphide C3P4