In which of the following pairs, the ions are iso electro n ic ?

1.	In which of the following pairs, the ions are iso electro n ic ?
Answer» `Na^(+), Mg^(2+)` `Al^(3+) , O^(-)` `Na^(+) , O^(2-)` `N^(3-), Cl^(-)` Solution :For, `N^(a+) = 11 - 1 = 10^(e-) Mg^(2+) = 12 - 2 = 10^(e-)` So, they have sam e num ber of electrons. For, `Al^(3+) = 13 - 3 = 10^(e-),O^(-1) = 8 + 1 = 9e^(-1)` They do not have sam e n u m b ER of electrons.For, `N^(a+) = 10^(e-) , O^(2-) = 8 + 2 = 10e^(-)` They have sam e num ber of electrons. For, `N^(3-) = 7 + 3 = 10 e , Cl^(-) = 17 + 1 = 18e^(-)`They do not have sam e num ber of electrons. So, Na+ is isoelectronic w ITH `Mg^(2+)` and `O^(2-)`

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