Question

A certain element emits Kα X-ray of energy 3.69 keV. Use the data from the previous problem to identify the element.

Answer 1

A certain element emits Kα X-ray of energy 3.69 keV is calcium.

Explanation:

Given:

Kα X-ray’s energy, E = 3690 eV

Wavelength λ is shown as

λ = hcEλ = 0.33658 nm

⇒λ= $0.34 \times 10-9 \mathrm{m}$

According to the Moseley’s equation,

cλ = a(Z-b)

where, c = light’s speed

λ = light’s wavelength  

Z = element’s atomic number

When the respective values are substituted,  

$3 \times 10-9 \times 1080.34$ = 107(Z-1.39) $\times$ 5

$\Leftrightarrow 8.82 \times 1017$ =$5 \times 107$(Z-1.39)

⇒93.95 = Z - 1.39 ⇒Z = 20.17 = 20

So, the element is found to be calcium.