Answer to Question #75649 in Inorganic Chemistry for Vikas

Question

How does the electronic configuration of ions vary with the configuration of their isoelectronic atoms? Who can explain with two examples and indicate the electronic configuration of ions along the series?

Answer 1

When you create an ion, you are either adding electrons to, or removing electrons from, the highest occupied energy subshell in the atom.
Explanation:
NONMETALS
Write the electronic structure for the neutral atom.
Then add electrons to the highest occupied subshell.
E.g., for Cl-:
Cl: 1s22s22p63s23p5 , but Cl- has one more electron.
Add it to the 3p subshell.
Cl⁻: 1s22s22p63s23p6 .
S AND P BLOCK METALS
Write the electronic structure for the neutral atom. Then remove electrons from the highest subshell.
For Na+:
Na: 1s22s22p63s1 , but Na+ has one less electron.
Take it from the 3s subshell.
Na+: 1s22s22p6
D BLOCK METALS
Remove s electrons before d electrons.
E.g., for Cr3+:
Cr: 1s22s22p63s23p64s13d5
Cr3+: 1s22s22p63s23p63d3
You remove the 4s electron first, followed by two of the 3d electrons.