INTERMOLECULAR FORCES
At this point in our study of the states of matter, we will stop to look more
closely at the attractive forces that exist between molecules. These
intermolecular forces (IMF) are responsible for many of the physical properties
of matter, such as boiling point. Intermolecular forces are typically due to the
attraction between the positively charged portion of one molecule and the
negatively charged portion of a nearby molecule. The positively and negatively
charged parts of a molecule are called dipoles, and are symbolized by (δ−) and
(δ+). While all intermolecular forces are caused by dipole attraction, they can be
further divided into three specific categories.
Forces of Attraction
These forces of attraction
are present between
molecules throughout
the water sample,
holding it together.
1) Hydrogen BondingThe attractive forces that exist between water molecules (shown above) are a
special type of intermolecular force called hydrogen bonds. Hydrogen bonds
occur whenever hydrogen is bonded to F, O, or N. These are the three most
electronegative elements, and as such, they “hog” electrons so much that the
hydrogen bonded to them are essentially naked protons, unshielded on the side
facing away from the bond. This positive, naked proton is attracted to the