x-ray crystallography

Examples of x-ray crystallography in the following topics:

• Determining Atomic Structures by X-Ray Crystallography

  • X-ray crystallography is a method of determining the arrangement of atoms within molecules.
  • X-ray crystallography is a method for determining the arrangement of atoms within a crystal structure.
  • X-ray crystallography is a powerful tool that has broad applications in the determination of the structures of both organic and inorganic compounds.
  • Throughout the history of chemistry and biochemistry, x-ray crystallography has been one of the most important methods in helping scientists understand the atomic structure and bonding.
  • Describe the method of x-ray crystallography as it is used for determining the structure of molecules.

• Oxidation States of Nitrogen

  • Thus, site-directed spin labeling (SDSL) has emerged as a valuable technique for mapping elements of secondary structure, at the level of the backbone fold, in a wide range of proteins, including those not amenable to structural characterization using classical structural techniques, such as nuclear magnetic resonance and X-ray crystallography.

• Electromagnetic Spectrum

  • Generally, electromagnetic radiation is classified by wavelength into radio wave, microwave, terahertz (or sub-millimeter) radiation, infrared, the visible region we perceive as light, ultraviolet, X-rays, and gamma rays.
  • X-rays: Excitation and ejection of core atomic electrons, Compton scattering (for low atomic numbers).
  • High-energy gamma rays: Creation of particle-antiparticle pairs.
  • Wave number = 1/wavelength in cm Speed of light = wavelength x frequency Energy = Planck's constant x frequency.
  • Dr Atkinson soon moved on to the un-needed gamma rays and improved them to delta rays!

• Modes of Radioactive Decay

  • Alpha particles carry a positive charge, beta particles carry a negative charge, and gamma rays are neutral.
  • Other experiments showed the similarity between classical beta radiation and cathode rays; they are both streams of electrons.
  • Likewise, gamma radiation and X-rays were found to be similar high-energy electromagnetic radiation.
  • Some decay reactions release energy in the form of electromagnetic waves called gamma rays.
  • Gamma rays can only be reduced by much more substantial mass, such as a very thick layer of lead.

• The Electromagnetic Spectrum

  • This electromagnetic spectrum ranges from very short wavelengths (including gamma and x-rays) to very long wavelengths (including microwaves and broadcast radio waves).

• Amorphous Solids

  • At an atomic scale, it is difficult to distinguish between the two different types, even using advanced analytical techniques such as x-ray diffraction and transmission electron microscopy.

• Isotopes in Medicine

  • This process is unlike a diagnostic X-ray, where external radiation is passed through the body to form an image.

• Nuclear Binding Energy and Mass Defect

  • When a large nucleus splits into pieces, excess energy is emitted as photons, or gamma rays, and as kinetic energy, as a number of different particles are ejected.
  • 1.86564 amu x $\frac{1\ kg}{6.02214\times10^{26}\ amu}$ = 3.09797 x 10-27 kg
  • $2.7843\times10^{-10}\frac{Joules}{atom}\ \times \frac {6.02\times10^{23}\ atoms}{mole}\times \frac{1\ kJ}{1000\ joules} =$ 1.6762 x 1011$\frac{kJ}{mole}$

• Millikan's Oil Drop Experiment

  • Alternatively, charge could be induced by including an ionizing radiation source (such as an X-ray tube).
  • Millikan found that all drops had charges which were multiples of 1.6 x 10-19 C.
  • Experimenting with cathode rays in 1897, J.

• The Atomic Bomb

  • Here, their motion is converted into X-ray heat, a process which takes about a millionth of a second.
  • This X-ray energy produces the blast and fire which are normally the purpose of a nuclear explosion.