In each of the following pairs, choose the species with the larger radius.
1) S^4+ or S^2+
2) S or S^2-
Adding electrons to an outside shell increases the radius (because the added electrons, each having the same negative charge, repel each other). Taking electrons away, obviously, makes the radius smaller.
s^2-
To determine which species in each pair has the larger radius, we need to consider their electronic configurations and the trends in the periodic table.
1) S^4+ or S^2+:
To compare the radii of these two species, we need to look at their electronic configurations.
- S^4+: The electronic configuration of S^4+ is 1s^22s^22p^63s^23p^6. When sulfur loses four electrons to form S^4+, its outermost electron shell becomes 3s^23p^2.
- S^2+: The electronic configuration of S^2+ is 1s^22s^22p^63s^23p^6. When sulfur loses two electrons to form S^2+, its outermost electron shell also becomes 3s^23p^2.
Since both S^4+ and S^2+ have the same electron configurations, they have the same number of electrons in their outermost shell. Therefore, their sizes will be similar. In this case, it is reasonable to assume that S^2+ has the larger radius since it has lost fewer electrons. So, S^2+ has a larger radius than S^4+.
2) S or S^2-:
Again, we need to compare the electronic configurations of these two species.
- S: In its neutral state, sulfur (S) has the electronic configuration 1s^22s^22p^63s^23p^4. It has six electrons in the outermost shell.
- S^2-: Sulfur can gain two electrons to become S^2-. In this case, its electronic configuration becomes 1s^22s^22p^63s^23p^6, which means there are eight electrons in the outermost shell.
As we move from S to S^2-, the number of electrons in the outermost shell increases from six to eight. Since the number of electrons in the outermost shell determines the size of the atom, S^2- has a larger radius than S. Therefore, S^2- has a larger radius than S.
In summary:
1) S^2+ has a larger radius than S^4+.
2) S^2- has a larger radius than S.
Remember that when comparing atomic radii, we look at the electron configurations and the number of electrons in the outermost shell.