(Polar molecules, Non-polar molecules, etc.)
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What is the difference between the polar and non-polar molecules in regards to dipole movement? I know in lecture, Professor Lavelle was talking about polar bonds that either cancel out dipoles or did not, but I was a little confused about the concept.
Basically, the dipole moment occurs whenever there is a more electronegative molecule within a covalent bond. For example, h2o is a polar molecule because oxygen is way more electronegative then hydrogen; thus the dipole moment occurs as the hydrogen shares its electrons with oxygen and gets a slightly positive charge and the oxygen gets a slightly negative charge.
When a molecule has no dipole moment(the dipole moment is symmetric), it is nonpolar ( for example, CO2). To be considered as a polar molecule, the difference in electronegativity of the atoms must be large. Using the water molecule as an example, the vertical components of the dipole moment points in the direction of oxygen, which makes the net dipole moment that points towards the oxygen and makes the oxygen more negative.
In addition to this, an easy way to identify polarity (or its absence) in a Lewis structure is to see whether a single central atom in surrounded by any number of identical surrounding atoms (such as in tetrahedral, trigonal planar, octahedral, etc..). In these, each surrounding atom pulls electrons toward themselves (creating a dipole); however, since all the atoms have equal electronegativity their dipoles should be equal in charge and thus cancel each other out. In this way, a molecule can have dipoles that cancel to become an overall nonpolar molecule.
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