What term describes an imperfection or deviation from the ideal arrangement of atoms along a line in the crystal lattice?

• A. Graining
• B. Growth Marks
• C. Habit
• D. Line Defect (Dislocation)

Answer: (D)

The main idea here is a dislocation, a line defect in the crystal lattice. Crystals are built from atoms in an orderly arrangement, but imperfections can occur. A line defect describes a disruption that runs along a line through the lattice, altering how atoms are packed along that path. The most common forms are edge dislocations, where an extra half-plane of atoms introduces distortion along the line, and screw dislocations, where the lattice planes spiral around the defect line. These defects differ from surface or shape features: graining refers to the boundaries between different crystal grains, growth marks are surface irregularities from how the crystal grew, and habit describes the overall external shape of the crystal. Since a line defect specifically denotes an imperfection along a line within the lattice, it’s the correct term.