What will rubidium-83 will decay into by electron capture?
Rubidium-83 will decay into krypton-83 by electron capture.
Electron capture is a process in which a proton in the nucleus captures one of the inner electrons and forms a neutron.
₁¹H + ₋₁⁰e → ₀¹n
Since a proton becomes a neutron, the number of protons decreases by 1, but the atomic mass stays the same.
Thus, the equation for electron capture in the decay of rubidium-83 is
₃₇⁸³Rb + ₋₁⁰e → ₃₆⁸³Kr
Hope this helps.