In metal bonding, what is shared among all participating atoms?

In metal bonding, what is fundamentally shared among all participating atoms are the valence electrons. Metals tend to have a small number of valence electrons that they can easily lose, resulting in a 'sea of electrons' that are free to move throughout the metallic lattice. This electron sharing and delocalization among many atoms give metals their characteristic properties, such as electrical conductivity and malleability.

The valence electrons are essential in forming metallic bonds because they allow multiple metal atoms to interact and hold together in a cohesive structure. This is in contrast to options like nuclei, protons, or neutrons, which are not shared in the same way. The nucleus of each atom is a unique entity that is not shared among surrounding atoms. Protons, which reside in the nucleus, determine the identity of the element and do not participate in bonding. Neutrons, found alongside protons in the nucleus, contribute to the atomic mass and stability of the nucleus, but they do not play a role in the formation of metallic bonds.

Therefore, the sharing of valence electrons is key to the concept of metallic bonding, allowing metals to maintain their structural integrity and conductive properties.