The following demonstration shows that forces can exist even though objects actually are not in direct contact.
A paper clip can be suspended about two millimeters from the magnet. The thread is attached to the base of the ring stand with adhesive tape. A piece of paper may be passed between the paper clip and the magnet without disturbing the setup. A long hair may be substituted for the thread.
Figure 4. Force between a magnet and a paper clip.
Several different equations can be used to estimate the degree to which a chemical bond between two atoms is ionic or covalent. The electronegativity difference between the atoms, (xA - xB) is a central key. xA is the electronegativity of the more electronegative element. One of these equations was developed by the famous chemist, Linus Pauling. When this equation is plotted, it has the shape of a stretched-out S. Such a graph is shown in Figure 5 where fractional ionicity represents the fractional ionic character (a value of 1 indicates 100% ionic).
Figure 5. Pauling Fractional Ionic Character.
(Note: A full-page version of this graph is found in the Appendix; it may be used either as a student handout, a transparency master, or both.)
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