Vacancy diffusion involves an atom moving to which position?

• A. A neighboring interstitial site
• B. A neighboring vacancy
• C. A distant site in another lattice
• D. A surface site

Answer: (B)

In vacancy diffusion, atoms move by hopping into an adjacent empty lattice site. A neighboring vacancy is the empty site next to the atom, so the atom jumps into that spot and the vacancy shifts to the atom’s old position. This creates a chain of hops that lets atoms migrate through the crystal. It’s different from interstitial diffusion, where atoms move through interstitial spaces, and it’s not about migrating to distant sites or to surfaces. So the atom ends up moving into the neighboring vacant lattice site.