Answer:
Cl
Explanation:
⁴¹Ca has an atomic number equal to 20, it means that it has 20 protons and 20 electrons ad its neutral state. In the decay by electron capture, it will lose one electron and will become a cation, but the mass (41) and the atomic number will remain the same.
When Ca⁺ undergoes alpha decay, it will lose an alpha particle, which has mass 4 and 2 protons.
⁴¹₂₀Ca⁺ → ³⁷₁₈X⁺ + ⁴₂α
To be stable, X will lose a proton and will become ³⁷₁₇X. The element which has atomic number 17 is chlorine, Cl.
