Crystalline and Amorphous Material✓Crystalline material: atoms, molecules, or ions are arranged regularlyand periodically (long range order).✓Amorphous material: atoms, molecules, or ions arenotarranged regularlyand periodically (short range order).✓Crystalline materials are of two types:✓Single crystal: periodic and repeated arrangement ofatoms extends throughout the crystal.✓Polycrystal: collection of small crystals (grains orcrystallites).