Which term refers to a lattice imperfection created when an atom is missing from its lattice position?

• A. Strain
• B. Surface Graining
• C. Trigon
• D. Vacancy

Answer: (D)

A missing atom in a crystal lattice creates a vacancy defect, a type of point defect. When an atom is absent from its lattice site, the site remains empty and disrupts the regular arrangement of the surrounding atoms. This vacancy can influence properties like diffusion (atoms move by jumping into empty sites) and, in diamonds, can interact with impurities to form color centers that affect color. Strain describes distortions in the lattice due to stress rather than a missing atom; surface graining relates to growth-related surface features; and a term like trigon isn’t the standard label for a lattice vacancy. So the term that best fits “a lattice imperfection created when an atom is missing from its lattice position” is vacancy.