How Do We Know the Structures of Crystals

Virtually all we know about crystal structure has been learned from X-ray diffraction studies. X-ray diffraction is the scattering of X rays by the units of a crystalhne solid. The scattering, or diffraction patterns, produced are used to deduce the arrangement of particles in the solid lattice. 

Max Theodor Felix von Laue (1879-1960). German physicist. Von Laue received the Nobel Prize in Physics in 1914 for his discovery of X-ray diffraction. 

X rays of wavelength 0.154 nm strike an aluminum crystal the rays are reflected at an angle of 19.3° Assuming that n = 1, calculate the spacing between the planes of aluminum atoms (in pm) that is responsible for this angle of reflection. 

Practice Problem B At what angle will X rays of wavelength 0.154 nm be diffracted from a crystal if the distance (in pm) between layers in the crystal is 188 pm (Assume n = 1.) 

154 pm = = 233 pm 2sm0 2sml9.3 between layers of atoms in a crystal should be similar in magnitude to the wavelength 

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