Home > Uncategorized > Introduction to Solid State Chemistry Lecture 12: Secondary Bonding

Introduction to Solid State Chemistry Lecture 12: Secondary Bonding

Overview
This is a very nice lecture at 35 minutes.

Details
Is something a solid, liquid, or gas?
Secondary bonding is aggregate bonding.

Ionic bonding leads to crystal formation in ion arrays. Covalent bonding leads to molecules like HCl or 3D networks like diamond.

Cohesive force versus disruptive force (thermal)

HCl is a polar covalent molecule. How does one HCl interact with another HCl? That determines phase. Intramolecular primary bonds are the H-Cl bond. Intermolecular bonding governs aggregation. The primary bond is inside the molecule.

Secondary bonds come in three flavors. Dipole dipole interactions occur only between polar molecules. The energy = dipole^4/(seperation^3)1/Temperature. 5 kJ/mol.
Operates at low temperatures. Mp = -115C, BP = -85C.
787 kJ/mol is the crystallization energy of NaCl.

Induced dipole/induced dipole is operative in non-polar species. Ar mp 84k, bp 87k. I2, CH4. How do argons bond? THe electrons are in motion leading to time flucating dipoles. London in 1930 was the first to explain this. London dispersion force or VdW. Here it is the primary bonding. E = polarizability(polarizabilty-ease of electron displacement, size, corral, is smaller, number of electrons, how tightly they are held.)^2/(seperation)^6.

At room temp, propane is a gas. Octane has a bigger canal and is a liquid.

Propane MW 44, mp -190 bp -42 gas at RT.
Octane MW 114 mp-57 bp125 liquid at RT.
Eicosane is C20H42 MW 282 mp 37C bp 343 solid at RT.
Hydrogen bonding occurs between H and NOF. A nonbonding pair occupies alot of space as it is unconstrained.
H-F…H-F. The H in HF is proton like.

AVEE average valence electron energy.

Element AVVE AVVE-EN EN
F 24 4.2 3.98
O 20 3.61 3.44
N 19 3.07 3.04
Cl 17 2.87 3.16
Br 16 2.69 2.96

When looking at homologous series, if lighter atoms have higher energy than expected, might by H bonding or dd.

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Categories: Uncategorized
  1. Hyperborean
    January 23, 2013 at 2:39 pm

    WN education? BRILLIANT IDEA!

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