Dipole moment in chemistry

\( \newcommand\) • • • • • Dipole moments occur when there is a separation of charge. They can occur between two ions in an ionic bond or between atoms in a covalent bond; dipole moments arise from differences in electronegativity. The larger the difference in electronegativity, the larger the dipole moment. The distance between the charge separation is also a deciding factor into the size of the dipole moment. The dipole moment is a measure of the polarity of the molecule. Dipole Moment When two electrical charges, of opposite sign and equal magnitude, are separated by a distance, a dipole is established. The size of a dipole is measured by its dipole moment (\(\mu\)). Dip ole moment is measured in Debye units, which is equal to the distance between the charges multiplied by the charge ( 1 Debye equals \(3.34 \times 10^\] Example \(\PageIndex\right)=1.84\; D\] Polarity and Structure of Molecules The shape of a molecule and the polarity of its bonds determine the OVERALL POLARITY of that molecule. A molecule that contains polar bonds, might not have any overall polarity, depending upon its shape. The simple definition of whether a complex molecule is polar or not depends upon whether its overall centers of positive and negative charges overlap. If these centers lie at the same point in space, then the molecule has no overall polarity (and is non polar). If a molecule is completely symmetric, then the dipole moment vectors on each molecule will cancel each other out, making...

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Example: Calculate the dipole moment of a water molecule. Since the bond moment of the O-H bond is -1.5 Debyes. The H−O−H bond angle of water is pretty much 104.5 degrees. Then we divide 104.5 by 2 to get 52.25 degrees for each side, then imagine two right angles. With that, and the fact that cosθ=cos(−θ). Therefore, our left contribution will be; = 1.5 x cos ( -52.25 ) = 0.918 And our right contribution will be the same as the left contribution. = 0.918 Finally, we sum them up. = 0.918 + 0.918 = 1.836 D

I'm a physics professor who often teaches students who have taken a lot of chemistry (read: pre-meds). In physics, the dipole moment of a charge configuration is defined as pointing from concentrations of negative charge towards concentrations of positive charge. This is embodied in the formula we use for the dipole moment of a charge configuration, $$ \vec = 0$) and a charge of $+e$ a distance $d$ away, this formula yields a vector that points from the negative charge to the positive charge, with magnitude $ed$. However, the first time I taught this material in a class with a large number of chemistry students, they were very confused; they had always learned that the dipole vector of a polar molecule points from positive charge towards negative charge, i.e., in the opposite direction of the convention from physics. For example, by the physics convention, the dipole moment of the water molecule points away from the point of the "V" formed by the bonds, while under the chemistry convention, the dipole moment points in the direction of the point of the "V". How did this convention arise? Is there an advantage to defining the dipole vectors this way in chemistry calculations? Or is it one of those scientific conventions that someone wrote down one point, and got ingrained in textbooks ever since? (Is it One of the answers to $\begingroup$ @user1420303 - The vector style notation you are using is from the US being first published in the textbook 'vector analysis' in 1901. In ...

Helmenstine, Anne Marie, Ph.D. "Dipole Definition in Chemistry and Physics." ThoughtCo, Aug. 29, 2020, thoughtco.com/definition-of-dipole-605031. Helmenstine, Anne Marie, Ph.D. (2020, August 29). Dipole Definition in Chemistry and Physics. Retrieved from https://www.thoughtco.com/definition-of-dipole-605031 Helmenstine, Anne Marie, Ph.D. "Dipole Definition in Chemistry and Physics." ThoughtCo. https://www.thoughtco.com/definition-of-dipole-605031 (accessed June 15, 2023).

• Chemistry • Physical Chemistry • Dipole Moment Dipole Moment Have you ever tried to force two same-charged magnets together? Even with all your might, magnets of the same charge will always repel, even if you try to squeeze them together. However, magnets with opposite poles can snap together easily. Magnets aren't the only things that can do this, molecules can too! Molecules with a dipole can attract or repel other molecules.… Dipole Moment • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • Have you ever tried to force two same-charged magnets together? Even with all your might, magnets of the same charge will always repel, even if you try to squeeze them together. Howe...