Chapter 11: Lewsin Model, Bonds PDF

Preview

Summary

The Lewis model, bonding and structures and how you make your own Lewis models...

Description

Announcements - Mastering Chemistry Registration on Canvas - PTtable.com Chapter 11: *Bond angles can vary from the idealized angles because double and triple bonds occupy more space than single bonds, and lone pairs occupy more space than bonding groups. Lone pairs take up the most space Shapes of Larger Molecules - For larger molecules, look at the geometry about each atom rather than the molecules as a whole Polarity of Molecules - Covalent Bond: formed between two non-metals that have similar electronegativities. More sharing of electron bonds - Ionic Bond: formed between a metal and a nonmetal. - Nonpolar Bonds: form between two atoms that share their electrons equally (i.e CO2) - Polar Bonds: form when two bonded atoms share electrons unequally. (i.e polar) - Electronegativity: is a measure of an atom's ability to attract shared electrons to itself. On the periodic table, electronegativity generally increases as you move from left to right across a period and decreases as you move down a group. - Bond Dipoles: The partial charges assigned to bonded atoms due to differences in electron density caused by electronegativity, inductive effects, and other factors.

-

A is the first element, B is the second element plus subscript, E is # of electrons

Polarity and Solubility: Like dissolves Like - Polar molecules are attracted to other polar molecules - Because water is a polar molecule, other polar molecules dissolve well in water, and most ionic compounds as well - Some molecules have both polar and nonpolar parts (i.e lipids, they have polar heads or polar sections and a nonpolar tail) The Lewis Model

Pros Cons -

Predicts trends in properties but does not give good numerical predictions, (i.e bond strength and bond length) Gives good first approximations of the bond angles in molecules but usually cannot be used to get the actual angle Cannot write one correct structure for many molecules where resonance is important Often does not predict the correct magnetic behavior of molecules (i.e O2 is paramagnetic, although the lewis structure predicts it is diamagnetic)...