For light elements, what is the ratio of neutrons to protons that predicts a stable nucleus?

The neutron–proton ratio also called as nuclear ratio is the ratio of the number of neutrons to the number of protons of a nucleus.The ratio generally increases with increasing atomic number on stable nuclei. Stable nuclei are generally elements that have atomic numbers below Uranium (92).

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na