Dipole vs Induced Dipole

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Dipole vs Induced Dipole

Postby Caitlin_Murphy_3C » Sun Nov 11, 2018 11:35 am

what is the difference between a dipole and an induced dipole? How do their bond properties vary?

Chris Freking 2G
Posts: 60
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Re: Dipole vs Induced Dipole

Postby Chris Freking 2G » Sun Nov 11, 2018 11:47 am

A dipole is a molecule with opposite charges on both ends (positive on one side, negative on the other side). For example, H2O is a dipole as the hydrogens have a partial positive charge and the oxygen has a partial negative charge.

An induced dipole is the result of two molecules interacting and causing one of the molecules' electrons to have this distorted charge. For example, in HCl, the hydrogen is strongly positive and the Cl is strongly negative. If that molecule interacts with a nonpolar molecule like N2, the charges of HCl are strong enough to distort the electrons in N2 so that it becomes an induced dipole.

Maharsh Patel 4E
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Joined: Fri Sep 28, 2018 12:27 am

Re: Dipole vs Induced Dipole

Postby Maharsh Patel 4E » Sun Nov 11, 2018 12:11 pm

A dipole occurs when you have a polar molecule that has two opposite charges. For example H2O has a dipole because there are polar bonds between the hydrogen and oxygen, making oxygen slightly positive and hydrogen slightly negative. An induced dipole can occur in any molecule (polar or nonpolar) and is a result of the movement of electrons. At any given point in time, the electron density of one atom/molecule can greater at one end of the atom, causing it to have a slightly negative charge and a slightly positive charge. This will distort the electron cloud of neighboring atoms/molecules and cause these molecules to have a slightly negative and positive charge. The charges in induced dipoles are only momentary and last a very short time while those in dipoles are constant and are always present.

David S
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Joined: Fri Sep 28, 2018 12:15 am

Re: Dipole vs Induced Dipole

Postby David S » Sun Nov 11, 2018 12:56 pm

A Dipole refers to a molecule that has a true and constant Dipole moment. Polar molecules, due to electronegativity differences between constituent atoms, will have permanent partial positive and partial negative regions. When these partial charge regions are oriented such that the resulting dipoles don't cancel out, the molecule will have a permanent net Dipole.

An induced Dipole refers to molecules that do not typically meet the conditions above necessary for having a true Dipole, but, when around other molecules, develop temporary dipoles. When ions and/or molecules with a true dipole are near such molecules, their electrostatic influence will induce the distortion of that molecule's electron cloud, making it have a temporary dipole. Between multiple molecules without dipoles, random fluxuations within electron clouds result in the formation of weak and temporary dipoles which have a chain effect on the electron clouds of surrounding molecules.

In terms of strength, intermolecular interactions involving true dipoles and/or ions are typically stronger than their counterpart intermolecular interactions involving induced dipoles and/or ions. This results in substances with true dipole and or ions interactions being more resistant to temperature change and possessing higher boiling and melting points.
However, it is important to note that with London dispersion forces, increasing polarizability and size of molecules, as well as a shape allowing for molecules to have more surface area in close proximity greatly influence the strength of the dispersion forces. This can result in cases where dispersion forces can be stronger than dipole-dipole interactions.

Note however, that these types of intermolecular forces arent mutually exclusive; for example, specimen that exhibit stronger IMFs such as hydrogen bonding also exhibit weaker IMFs such as dipole-dipole interactions and dispersion forces.

Here's a little reference chart for the forces:
https://www.chem.fsu.edu/chemlab/chm104 ... mmary3.gif
(^note: energy ranges are in kJ/mol)

Additional resources:
https://www.chem.wisc.edu/deptfiles/gen ... f/imf5.htm

Return to “Interionic and Intermolecular Forces (Ion-Ion, Ion-Dipole, Dipole-Dipole, Dipole-Induced Dipole, Dispersion/Induced Dipole-Induced Dipole/London Forces, Hydrogen Bonding)”

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