13.4.4: Pauling’s Fourth Rule
- Page ID
- 18354
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Pauling’s fourth rule is an extension of his third, stating that small cations with high charges do not share anions easily with other cations. This is another consequence of the fact that highly charged cations will repel each other. For example, all silicate minerals contain Si4+ tetrahedra. Yet in all the many known silicate minerals, none contains (SiO4)4– polyhedra that share edges or faces because that would bring Si4+ cations too close together.