Question 12 Marks
In each of the following pairs of salts, which one is more stable?
1. Ferrous and ferric salts
2. Cuprous and cupric salts
1. Ferrous and ferric salts
2. Cuprous and cupric salts
Answer
View full question & answer→1. Ferrous and ferric salts In ferrous salts $Fe ^{2+}$, the configuration is $1 s^2 2 s^2, 2 p ^6, 3 s^2, 3 p ^6, 3 d^6$. In ferric salts $Fe ^{3+}$, the configuration is $1 s^2 2 s^2, 2 p^6, 3 s^2, 3 p^6, 3 d^5$.
As half-filled $3 d^5$ configuration is more stable therefore ferric salts are more stable than ferrous salts.
2. Cuprous and cupric salts In cuprous salts, the configuration of $Cu ^{+}$is $1 s^2 2 s^2 2 p ^6 3 s^2 3 p ^6 3 d^{10}$.
In cupric salts, the configuration of $Cu ^{2+}$ is $1 s^2 2 s^2, 2 p^6, 3 s^2, 3 p^6, 3 d^9$. Although $Cu ^{+}$has completely filled d-orbital, yet cuprous salts are less stable. This is because the nuclear charge is not sufficient enough to hold 18 electrons of $Cu ^{+}$ion present in the outermost shell.
As half-filled $3 d^5$ configuration is more stable therefore ferric salts are more stable than ferrous salts.
2. Cuprous and cupric salts In cuprous salts, the configuration of $Cu ^{+}$is $1 s^2 2 s^2 2 p ^6 3 s^2 3 p ^6 3 d^{10}$.
In cupric salts, the configuration of $Cu ^{2+}$ is $1 s^2 2 s^2, 2 p^6, 3 s^2, 3 p^6, 3 d^9$. Although $Cu ^{+}$has completely filled d-orbital, yet cuprous salts are less stable. This is because the nuclear charge is not sufficient enough to hold 18 electrons of $Cu ^{+}$ion present in the outermost shell.
