" Which of two ions "Ca^(2+)" (or) "Zn^(2+)" is more stable and why? "

Which of the two ions Ca^(2+) " or " Zn^(2+) is more stable and why ?

Which one is more stable and why?

Which of the two ions, Ca^(2+) and Zn^(2+) is more stable? Why? For ionic substances which is the proper term to use 'Formula weight' or "Molecular weight'?

Which of two : O_2N < H_2CH_2O or CH_3CH_2O^(-) is more stable and why?

Which out of H_(2)^(-) and H_(2)^(+) is more stable and why?

Out of Cu_(2)Cl_(2) , which is more stable and why ?