Answered

The atomic symbol mc025-1.jpg represents potassium-40 (K-40), a radioactive isotope that has 19 protons and 21 neutrons. Which atomic symbol could represent an isotope that results from the decay of K-40?

A40 Ar

18

B40 K

18

C42 Ca

20

D42 K

20

Verified Answer :

The answer is a 40/18Ar

Answer: The correct option is A.

Explanation: For a radioactive isotope of potassium, which is \(^{40}K\) having 19 protons and 21 neutrons, the decay processes are beta-decay and electron capture.

Potassium-40 undergoing decay processes:

  • Electron Capture: In this process, the unstable nuclei becomes stable by converting electron into neutron with the help of proton.

\(_{19}^{40}\textrm{K}\overset{\text{electron capture}}{\rightarrow} _{18}^{40}\textrm{Ar}\)

  • Beta-decay: In this process, the unstable nuclei becomes stable by converting a neutron into proton and electron.

\(_{19}^{40}\textrm{K}\overset{\beta \text{-decay}}{\rightarrow} _{20}^{40}\textrm{Ca}\)

From the two processes, the K-40 isotope forms \(_{18}^{40}\textrm{Ar}\) by electron capture. So, the correct option is A.

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