(B) Atoms and ions having the same number of electrons are isoelectronic.Neon $(Ne)$ has an atomic number of $10$,so it has $10$ electrons.SpeciesNumb

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(B) Atoms and ions having the same number of electrons are isoelectronic.Neon $(Ne)$ has an atomic number of $10$,so it has $10$ electrons.SpeciesNumber of electronsNeon $(Ne)$$10$$O^{2-}$$8 + 2 = 10$$Na$$11$$Mg^{2+}$$12 - 2 = 10$$Al^{3+}$$13 - 3 = 10$Since $Na$ has $11$ electrons,it is not isoelectronic with neon.