Passage I

X-ray spectroscopy is a way of analyzing a mineral's composition. When an electron beam is directed onto a mineral, each element in the mineral emits characteristic X-rays having a narrow range of energies. The intensityof all X-rays emitted by the elements is measured. The greater the maximum intensity of the X-rays emitted by an ele­ment, the greater the relative concentration of the element in the mineral.

Figures 1 and 2 show X-ray spectroscopy results for Mineral 1 and Mineral 2, respectively, under identical con­ditions. Energy is given in kiloelectron volts (keV); inten­sity is given in counts per second (sec).

3. The energy of the most intense X-rays emitted by an element is directly related to the element’s atomic number. The atomic numbers of several of the elements are shown in the table below.

If an element with an atomic number of 22 had been present in Mineral 1, the energy of the most intense X-rays emitted by this element would most likely have been:

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

The atomic mass of the element mentioned in the question stem is directly related to the intensity emitted. It can be seen from the table in the title that the element with an atomic mass of 22 is between Ca and Cr, so the intensity emitted should also be between Ca and Cr. From figure 1, it can be seen that the energy is in the range of 3.5 keV-5.5 keV