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What are conduction electrons in a metal crystal?

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A rough, translucent yellow crystal of elemental sulfur displayed against a solid black background. — crystal A crystal form of elemental sulfur. Sulfur has an atomic weight of about 32.06 atomic mass units (amu), which means that its molar mass is 32.06 grams.

In a metal crystal, conduction electrons are valence electrons that have become nonlocalized, meaning they are no longer associated with any specific atom. When metal atoms form a solid, their outermost electron shells overlap, allowing these electrons to wander freely throughout the entire crystal structure.12

These mobile electrons are responsible for the high electrical and thermal conductivity of metals, as they are free to move when an electrical field is applied. The atoms that donate these electrons become positive ions, and the interaction between these ions and the surrounding sea of conduction electrons creates the metallic bond that holds the crystal together.12

While simple models, such as the one proposed by Arnold Johannes Wilhelm Sommerfeld, treat these electrons as free particles, their actual movement is influenced by factors like electron mobility, crystal purity, and the specific electronic structure of the metal, such as the presence of d-states in transition metals.32