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VSEPR and Polarity Since all atoms have different electronegativities, a “Tug of war ” for the electrons in a bond begins when atoms bond. When an atom bonds with another one of itself (example F-F), the difference in electronegativity is zero . This is known as nonpolar covalent or pure covalent bond. When an atom bonds with different atoms, they nonpolar covalent bonds, can be polar or _________ depending on the differences in electronegativities. What happen when the electronegativity isn’t equal large , an bonding When the difference in electronegativity is ionic electron is transferred and results. When the difference in electronegativity is very ____________, small (<0.5) the electrons are __________ shared ______ ____________ and nonpolar bonding results. equally When the difference in electronegativity is moderate , there is unequal sharing. Resulting in a polar covalent. As a result, the electrons spend more time around the more electronegative ( stronger ) atom, which negative makes it slightly . The weaker atom positive becomes slightly . This results in the polar bond being a dipole – two poles Polarity of Molecules Overall, molecules can be polar or non-polar , depending on the results of the molecular of war .” “ Tug If the VESPR shape makes it a symmetrical molecule then the result is nonpolar . asymmetrical If VESPR shape makes it a molecule then the result is polar . Let’s look at H2O polar , because its shape is Water is Asymmetrical (bent) A Dissolving Situation Ability of a substance to dissolve is based on polarity … like dissolves like . polar dissolves polar and nonpolar So, dissolves non-polar. Water is polar, so it dissolves polar substances Forces Ionic and covalent bonds are called intramolecular (within molecules) Intermolecula – between molecules – also called Van rder Waals forces – WEAK Intermolecular forces are always weaker than intramolecular forces. Types of van der Waal forces 2 Dipole-dipole interactions – between ___ polar covalent molecules _______ Dipole-induced dipole interactions – between 1 _______ polar and ___ 1 _________ ___ nonpolar covalent molecules 2 London’s Dispersion Forces – between ___ nonpolar ____________ covalent molecules H in one Hydrogen Bonding – between ___ N ___, O or ___, F in another molecule with ___, strong molecule. It is an unusually __________ bond.