We are all familiar with table salt, or sodium chloride (NaCl).
This essential, common compound is ordinarily crystalline and brittle in nature. However, many materials behave strangely
on the scale of minute quantities, and salt is no exception. Researchers at Boston College have explored tiny salt samples
at close distance using an atomic force microscope. This sensitive instrument detects small forces generated by the sample
molecules. When the microscope probe was directed within about seven nanometers (less than a millionth of an inch) of the
salt surface, a strong, unexpected attractive force developed. As a result, a tiny portion of the salt material stretched
out and touched the probe. This bridge shows that salt behaves elastically on the microscopic scale. Rather than the salt
crystal breaking into fragments, its surface atoms become wire-like.