X-ray Diffraction
Definition and meaning of X-ray Diffraction in chemistry.
X-ray diffraction is a powerful analytical technique used to determine the atomic and molecular structure of a crystal. It relies on the elastic scattering of X-ray photons by the electrons in the atoms comprising the sample.
In more detail
When a beam of X-rays strikes a crystalline material, the regularly spaced atoms act as a three-dimensional diffraction grating. This causes the X-rays to scatter in specific directions according to Bragg's Law. By measuring the angles and intensities of these scattered beams, scientists can construct a three-dimensional picture of the electron density within the crystal. This electron density map reveals the exact positions of the atoms, their chemical bonds, and various other structural details.
Key facts
| Field | Analytical Chemistry |
|---|---|
| Key equation | Bragg's Law |
| Primary use | Determining crystal structures |
X-ray diffraction was famously used by Rosalind Franklin to capture images of DNA, which proved crucial for identifying its double helix structure.
Frequently asked questions
Can X-ray diffraction be used on non-crystalline samples?
While standard X-ray crystallography requires ordered crystals, powder X-ray diffraction can be used to analyze polycrystalline materials and identify phase composition.
Why are X-rays used instead of visible light?
The wavelength of X-rays is roughly on the same scale as the distances between atoms in a crystal, which is necessary for diffraction to occur.