Particle clustering electrostatic charging

Figure 14-19 Stabilization of a colloid (Fe203 sol) by electrostatic forces. Each colloidal particle of this red sol is a cluster of many formula units of hydrated Fe203. Each attracts positively charged Fe + ions to its surface. (Fe + ions fit readily into the crystal structure, so they are preferentially adsorbed rather than the Cl ions.) Each particle is then surrounded by a shell of positively charged ions, so the particles repel one another and cannot combine to the extent necessary to cause acmal precipitation. The suspended particles scatter light, making the path of the light beam through the suspension visible.

It was also found that in the Pd cluster samples half of the metal particles carries an odd number of electrons and half an even number. Such an even-odd distinction was predicted by Kubo as a characteristic cluster property, but had never previously been observed. This might be understood in terms of classical electrostatics - it takes energy to put a charge g on a metal sphere of radius R. For... 

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