Properties favor melting and boiling points room a measure of how strong the attractive forces are between individual atom or molecules. (We contact these intermolecular forces – forces between molecules, together opposed come intramolecular pressures – pressures within a molecule. )

It every flows native this basic principle: as bonds become an ext polarized, the charges on the atoms end up being greater, which leads to higher intermolecular attractions, which leader to higher boiling points.

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There are four significant classes that interactions between molecules and they space all different manifestations of “opposite fees attract”.

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The four vital intermolecular forces are as follows:

Ionic bonds > Hydrogen bonding > Van der Waals dipole-dipole interactions > Van der Waals dispersion forces.

Let’s look at them individually, from the strongest to weakest.

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Table the Contents

1. Ionic forces

Ionic room interactions between charged atom or molecule (“ions”). Positively fee ions, such as Na(+) , Li(+), and Ca(2+), are termed cations. Negatively fee ions, such together Cl(–), Br(–), HO(–) are referred to as anions (I always got this straight through remembering that the “N” in “Anion” stood for “Negative”) The attractive forces between oppositely charged ion is described by Coulomb’s Law, in which the force increases through charge and also decreases as the distance in between these ions is increased. The very polarized (charged) nature of ionic molecule is reflect in your high melt points (NaCl has a melting allude of 801 °C) as well as in their high water solubility (for the alkali steel salts, anyway; steels that type multiple charges prefer to leaving residues on your bathtub)


5. Bottom Line

Boiling points space a measure up of intermolecular forces.The intermolecular pressures increase with enhancing polarization that bonds.The strength of intermolecular forces (and therefore affect on boiling points) is ionic > hydrogen bonding > dipole dipole > dispersionBoiling point increases v molecular weight, and also with surface ar area.

For one more discussion of these ethics see Chemguide

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