What is isotonic of Na+, be-2, b-3.

Dear Student, Isotone is defined as the elements having same number of neutrons. Here in the question, ions are given so ions vary in number of electrons therefore independent of neutrons. Thus the isotones of Na is Mg (both have 12 neutrons). Similarly, Beryllium and Boron have 5 neutrons. So they both are isotones of each other. Regards