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"Valence and Molecular Structure," Lectures 1 and 2. 1957. Produced for the Institutes Program of the National Science Foundation. Robert and Jane Chapin, producers. Lecture 1, Part 9. (2:03)

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Linus Pauling: This sort of valence, we can say that there is a chemical bond connecting the sodium ion with the six chloride ions that surround it in this crystal. This sort of valence is, I think, very well understood. The sodium ion here has a single positive charge. It is not attached to a chloride ion to form a sodium chloride molecule in the crystal. It is similarly related to all six of the chloride ions that surround it. I think that it is sensible to say that there is a one-sixth bond. One-sixth of an ionic bond between each sodium ion and each of the six chloride ions around it. And that the chloride ions itself with charge minus-one has its charge satisfied by the six one-sixth bonds that come to it from the six sodium ions that surround it.

Many substances can be discussed satisfactorily in terms of the ionic bond with transfer of electrons from one atom to another. On the other hand, there are many substances that can’t be discussed in this way. For example, the hydrogen molecule, H₂. Neither hydrogen atom picks up an electron from the other. Instead, the molecule has the structure shown here. The two electrons are held jointly by the two atoms; they constitute the bond between the two atoms. To form this sort of bond, the covalent bond, the bond that Professor G. N. Lewis of Berkeley called the chemical bond, we need to have an orbital for each of the two atoms and a pair of electrons.

During the next hour, we shall talk about the covalent bond and the structure of molecules containing bonds of this sort.

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Date: 1957
Genre: video
ID: 1957v.1
Copyright: More Information

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