As we know that atomic number is equal to number of protons = 11
Atomic mass number is equal to protons number + neutrons number = 11 + 12 = 23
An element with atomic number 11 and mass number 23 is Sodium.
But the species is not neutral because the number of protons are not equal to number of electrons.
10 electrons – 11 protons = 1 electron
It has excess 1 electron hence it is an anion.
So the symbol would be Na , 23 as superscript and 11as subscript