Consider the elemts ca, ba, as, and bi. which has
largest radius?
highest electronegativtity?
highest ionization energy?

Symbol      Element    Atomic Radius    Electronegativity     Ionization Energy
Ca          Calcium        194 pm                1                          57110 kJ/mol
Ba          Barium          253 pm                0.89                    3.6 x 10³ kJ/mol
As          Arsenic         114 pm                2.18                    12310 kJ/mol
Bi          Bismuth          143 pm               2.02                    8520 kJ/mol

Based on the above information.
The element with the largest radius is Ba.
The element with the highest electronegativity is As
The element with the hightest Ionization energy is Ca.

Well to my expert knowledge and my exquisite calculations i think the the negative ion # 412 is the key to sucess