When metal atoms bond to form a solid, what mainly contributes to their stability?

The stability of a solid metal structure primarily arises from the electron sea model, where a delocalized pool of electrons is shared among a lattice of metal cations. In metallic bonding, metal atoms release some of their electrons to form positively charged ions, or cations. These electrons are not associated with individual atoms but rather move freely throughout the metal structure, creating an "electron sea."

This free movement of electrons allows them to act as a glue that holds the metal cations together, providing both stability and electrical conductivity to the metal. The attractive forces between the positively charged metal ions and the negatively charged, delocalized electrons lead to a strong bond that enhances the overall structural integrity of the material.

While shared electrons in covalent bonds play a significant role in covalent compounds, that concept does not apply to metallic bonding, where the nature of bonding is quite different. Similarly, fixed positions of metal atoms relate more to crystalline structure but do not describe the bonding mechanism that contributes to stability in metals. Lastly, the repulsion among metal cations would actually work against stability, as it could lead to instability or even breakdown of the solid structure. Therefore, the electron sea shared among metal atoms is the key reason for their stability in solid form.