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Unformatted text preview: 13.1 Types of Chemical Bonds Spectroscopy = the study of the interactions of EM-Rad with matter Energy of interaction between a pair of ions can be calculated by using Coulombs Law o V = 2.31 x 10-19 J nm ( Q 1 Q 2 )/ r V = PE between 2 charges (joules) r = distance between the ion centers (nm) Q 1 and Q 2 = numerical ion charges o Negative sign indicates an attractive force The ion pair has lower energy than the separated ions o Attractive forces coming together go lower Amount you go down is V o Can also be used to calculate the repulsive energy when two like-charged ions are brought together (calculated energy will have a positive sign) Bonding between 2 identical atoms o Bonding occurs if the energy of the aggregate is lower than that of the separated atoms o Bond length = distance at which the energy is minimum (also: equilibrium internuclear distance ) At very short distances the energy rises steeply because of the great importance of the internuclear repulsive forces at these distances Zero reference point for energy atoms at infinite separation Polar Covalent Bonds o Unequal sharing of electrons in bonds 13.2 Electronegativity The ability of an atom in a molecule to attract shared electrons to itself Trend (for representative elements): increases bottom top and left right Range 4.0 for fluorine and 0.7 for francium For identical atoms, EN diff. = 0 e F are shared equally and no polarity occurs For atoms with widely differing EN, e- transfer usually occurs, producing ions Polarity of a bond increases as the difference in EN increases 13.3 Bond Polarity and Dipole Moments Dipole moment = = Q R o = Coulomb meter...
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