In which one of the following pairs the two species are both isoelectronic and isotopic? (Atomic num

Question

In which one of the following pairs the two species are both isoelectronic and isotopic? (Atomic numbers : $\mathrm{Ca}=20, \mathrm{Ar}=18, \mathrm{~K}=19, \mathrm{Mg}=12$, $\mathrm{Fe}=26, \mathrm{Na}=11$ )\

Professor PC Thomas Classes · Answer

(b) : ${ }^{39} \mathrm{~K}^{+}$and ${ }^{40} \mathrm{~K}^{+}$contains same number of electrons so they are isoelectronic. They have same atomic number but different mass numbers so they are also isotopes.\