A`K_(alpha)` X-ray emitted from a sample has an energy of `7.46 ke V. Of which element is the sample made?

Options

A. Calucium `(Ca, Z = 20)`
B. Cobalt `(Co, Z = 27)`
C. Cadmium `(Cd, Z = 48)`
D. Nickel `(Ni, Z = 28)`

Answer

D

Explanation

The energy of the `K_(alpha)` X-ray photon `E _(K_alpha) = E_(1) - E_(f) = (Z - 1)^(2) (- 3.4 eV + 13.6 eV)`
`= (Z - 1)^(2) (10.2 eV)`
Given `E _(K_alpha) = 7.46 keV`
`:. 7.46 xx 10^(3) eV = (Z - 1)^(2) (10.2 eV)`
or `(Z - 1)^(2) = (7.46 xx 10^(3))/(10.2) = 731.4`
or `(Z - 1) = 27 implies Z = 28`