Properties prefer melting and boiling points room a measure up of how strong the attractive pressures are in between individual atom or molecules. (We contact these intermolecular forces – forces between molecules, as opposed to intramolecular forces – forces within a molecule. )
It every flows indigenous this general principle: as bonds become much more polarized, the charges on the atoms end up being greater, which leader to greater intermolecular attractions, which leader to higher boiling points.
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There space four major classes the interactions in between molecules and they room all different manifestations the “opposite fees attract”.
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The four an essential intermolecular pressures are as follows:
Ionic bonds > Hydrogen bonding > Van der Waals dipole-dipole interactions > Van der Waals dispersion forces.
Let’s look in ~ them individually, from the strongest to weakest.
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Table the Contents
1. Ionic forces
Ionic space interactions in between charged atoms or molecules (“ions”). Positively charged ions, such as Na(+) , Li(+), and Ca(2+), space termed cations. Negatively fee ions, such as Cl(–), Br(–), HO(–) are referred to as anions (I constantly got this right through remembering that the “N” in “Anion” stood for “Negative”) The attractive forces in between oppositely charged ion is described by Coulomb’s Law, in which the pressure increases v charge and decreases as the distance between these ions is increased. The very polarized (charged) nature of ionic molecule is reflect in their high melting points (NaCl has a melting allude of 801 °C) and in your high water solubility (for the alkali metal salts, anyway; steels that form multiple charges choose to leave residues on your bathtub)
5. Bottom LineBoiling points space a measure up of intermolecular forces.The intermolecular forces increase with boosting polarization of bonds.The strength of intermolecular pressures (and therefore influence on boiling points) is ionic > hydrogen bonding > dipole dipole > dispersionBoiling suggest increases with molecular weight, and also with surface ar area.
For one more discussion the these ethics see Chemguide
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