Solution:
SOLUTION
Since the number of electrons is same in $$NO^{-}_{3}$$? and $$CO^{2-}_{3}$$ ? i.e. 32, therefore they are isoelectronic.
$$NO^{-}_{3}$$ -> no.of electrons = 7+(8×3)+1 = 32
$$CO^{2-}_{3}$$ -> no. of electrons = 6+(8×3)+2 = 32
Also, the geometry for both $$CO^{2-}_{3}$$? and $$NO^{-}_{3}$$? is sp2 and trigonal planar shape. Therefore, both are isostructural too.