The following table contains the wavelength, precision of measurement, and energy of the most useful characteristic x-ray lines for each element. In the table the first column lists the element, the characteristic line, and the atomic levels involved in the production of the x-ray photon. The middle columns give the wavelength (in Å* units) and the precision of measurement in the form of the probable error in the last digit. The last column gives the energy of the line in kiloelectron volts.