Final answer:
A delocalized electron is an electron that can move freely across different atoms, crucial for metallic bonding in metals. It's responsible for the electrical and thermal conductivity of metals and contributes to their luster and malleability.
Step-by-step explanation:
A delocalized electron is an electron in a molecule, ion, or solid metal that is not associated with any single atom or a covalent bond. In the context of metallic bonding, delocalized electrons originate from the outer energy levels of metal atoms and are free to move throughout the entire structure of the metal. This mobility of electrons is what forms the 'sea of electrons' and is fundamental to the metallic bond, in which these free electrons provide an attraction between the positively charged metal ions (or atomic kernels) and themselves. This delocalization is crucial for several characteristic properties of metals.
Metallic bonding, due to the presence of delocalized electrons, explains why metals are able to conduct electricity and heat effectively. It also gives metals their characteristic luster because delocalized electrons can absorb and re-emit photons of light. Moreover, the flexibility and strength in metals arise from their metallic bonds, as the electron 'sea' allows metal atoms to slide past each other without breaking the overall metallic structure.