The characteristic X ray lines of an element are produced when
Correct answer: B. an inner shell electron is knocked out and an outer electron falls in to fill the vacancy
- A. an outer electron is excited
- B. an inner shell electron is knocked out and an outer electron falls in to fill the vacancy
- C. the nucleus decays
- D. electrons are slowed by the target
Explanation
The energy gaps between inner shells are large, of the order of thousands of electron volts, so the photons emitted lie in the X ray region and their wavelengths are characteristic of the element. The continuous background, by contrast, comes from electrons being decelerated in the target. Moseley used these characteristic lines to establish atomic number as the ordering principle of the periodic table.
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About Atomic Spectra
Atoms emit or absorb light at specific wavelengths because electrons occupy quantized energy levels and change levels by absorbing or releasing photons. The topic covers emission and absorption spectra, spectral series, hydrogen’s line spectrum, energy-level transitions, and the relation between wavelength, frequency and photon energy.
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