Don't need the mass (23), but only the atomic number (11). The ion has 1 electron stripped, 10 remaining.
A sodium-23 atom with a +1 charge has 10 electrons, 11 protons, and 12 neutrons. The +1 charge indicates it has lost one electron compared to a neutral sodium atom. Sodium's atomic structure allows it to easily lose this electron to form a stable ion.
;