In metallic bonding, what causes a metal to lose its outer electrons and become an ion? I am trying to understand metallic bonding, atoms and ions.
For any reaction to happen/any bond to be created, the process has to be thermodynamically favourable, meaning the materials involved must acquire a more stable state via losing as much energy it possibly can. It is a fundamental characteristic of any spontaneous process in nature.
Here, while forming a metallic bond, the metal atoms lose their valence shell electrons to form the electronic configuration of a noble gas, which requires energy. After losing the electrons, the cations of the metal form a metal lattice, in which the electrons lost previously float. Now, the interaction between the electrons and the ions help stabilize the entire metal, releasing much energy. Thus released energy more than enough compensates for the required energy. And thus, the energy of the metal reduces, resulting in the formation of metallic bonds.
In short, metallic bond is formed because it is thermodynamically favourable. For more, read https://en.m.wikipedia.org/wiki/Metallic_bonding