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Posted: Fri Nov 24, 2017 3:31 pm
Does electronegativity have anything to do with VESPR models and if a molecule is polar or non-polar? Like, can we look at a periodic table and decide if a molecule is polar due to the elements included in it?
Posted: Fri Nov 24, 2017 3:37 pm
Yes! We take both the geometry of the molecule as well as the electronegativity of each atom in that molecule to determine polarity. We can use the periodic table and its trends to determine which atom is more electronegative than the other (but take note of the exceptions to this rule - such as the noble gases). Then, when we look at the lewis structure of the molecule, we can see if the "pull" of the more electronegative atom(s) cancels out due to the geometry. If it does, then the molecule is nonpolar, and if it doesn't, then the molecule is polar.
Posted: Sat Nov 25, 2017 10:55 pm
It's also important to note that 2 atoms (diatomic molecule) with a high difference in electronegagivity will form a polar bond. However, when you have a polyatomic molecule (multiple atoms bonding) symmetry and dipole moments cancelling determines whether a molecule is polar. For polyatomic molecules, atoms can form polar bonds but end up being non polar if the dipole moments cancel.
Posted: Sat Nov 25, 2017 11:28 pm
The general rule is that the farther away the elements are, the more polar, and the closer they are, the more nonpolar.