| Copper Sulfide |
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| CATEGORIES ABOUT COPPER SULFIDE | |
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QUANTUM CHEMISTRY It would seem that Cu2S is Cu+ ( D 10) monovalent cuprous sulfide, whereas CuS is Cu2+ (d9) cupric sulfide. However, this is not the case. Since the Cu2+ Ion is a relatively strong Oxidizer , it is able to oxidize sulfide to Disulfide ions: 2Cu2+ + 2S2- → 2Cu+ + 2S- → 2Cu+ + (S2)2- In this process the one missing d-electron ('' Electron Hole '') of the d9 configuration is transferred to the Sulfur . Sometimes that leads to sulfur pair formation sometimes not. The result is that Cu is essentially monovalent in all of the copper sulfides. What lies near the Fermi level is a Valence Band predominantly S 2p character. Most of the copper sulfides are Metal lic, as the pair formation is incomplete, so that the remaining holes in the valence band lead to Conductivity . For example, in CuS only two thirds of the sulfurs occur as pairs (disulfide ions). CuS2 is a special case, in that it has the pyrite structure. In this structure all sulfurs occur as pairs (disulfide ions). However because Cu is essentially Cu+, the disulfide ions are essentially (S-S)-1 rather than (S-S)-2. In other words there is an extra hole on the disulfide ion. As it is delocalized, this "pyrite" is metallic. By contrast the Mineral Pyrite (FeS2) consists of Fe2+ ions and (S-S)-2 ions and is a Semiconductor . EXTERNAL LINKS |
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