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4 Moderate to high melting temperatures.

5 Absorb very little light, producing transparent to translucent minerals with light colors and vitreous to sub‐vitreous lusters in macroscopic crystals.

metallic bond

Excellent examples of metallic bonding exist in the native metals such as native gold (Au), native silver (Ag), and native copper (Cu). Such materials are excellent conductors of electricity and heat. When materials with metallic bonds are subjected to an electric potential or field, delocalized electrons flow toward the positive anode, which creates and maintains a strong electric current. Similarly, when a thermal gradient exists, thermal vibrations are transferred by delocalized electrons, making such materials excellent heat conductors. When metals are stressed, the weakly held electrons tend to flow, which helps to explain the ductile behavior that characterizes native copper, silver, gold, and other metallically bonded substances.

ssss1 A model of metallic bonds with delocalized electrons (dark red) surrounding positive charge centers that consist of tightly held lower energy electrons (light red dots) surrounding individual nuclei (blue).