Properties favor melting and boiling points are a meacertain of how solid the attrenergetic forces are between individual atoms or molecules. (We speak to these intermolecular forces – forces between molecules, as opposed to intramolecular pressures – forces within a molecule. )

It all flows from this general principle: as bonds come to be even more polarized, the charges on the atoms come to be better, which leads to higher intermolecular attractions, which leads to higher boiling points.

You are watching: Identify the predominant intermolecular forces in each of the given substances.

There are 4 major classes of interactions in between molecules and also they are all various manifestations of “opposite charges attract”.

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MOC_Boiling_Point_Handout (PDF)

The 4 vital intermolecular pressures 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 strongest to weakest.

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Table of Contents

1. Ionic forces

Ionic are interactions between charged atoms or molecules (“ions”). Positively charged ions, such as Na(+) , Li(+), and Ca(2+), are termed cations. Negatively charged ions, such as Cl(–), Br(–), HO(–) are called anions (I always gained this right with remembering that the “N” in “Anion” stood for “Negative”) The attrenergetic pressures between oppositely charged ions is described by Coulomb’s Law, in which the pressure increases via charge and also decreases as the distance between these ions is enhanced. The highly polarized (charged) nature of ionic molecules is reflected in their high melting points (NaCl has actually a melting allude of 801 °C) and in their high water solubility (for the alkali steel salts, anyway; metals that form multiple charges like to leave residues on your bathtub)


5. Bottom Line

Boiling points are a meacertain of intermolecular pressures.The intermolecular forces rise through increasing polarization of bonds.The toughness of intermolecular forces (and also therefore influence on boiling points) is ionic > hydrogen bonding > dipole dipole > dispersionBoiling allude increases via molecular weight, and with surchallenge area.

For another conversation of these values watch Chemguide

Reminder – don’t forget the free boiling point examine guide (Contains all the key points debated in this post)