Question

How does the electronic configuration of ions vary with the configuration of their

isoelectronic atoms. Explain by taking two examples. 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

For Na+:

Na:1s22s22p63s, 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:1s22s22p63s23p64s3d5

Cr3+:1s22s22p63s23p63d3

You remove the 4s electron first, followed by two of the 3d electrons.

EXAMPLES

Write the electron configurations for O2-,Ca2+, and Zn2+.

Solutions

O:1s22s22p4

O2-:1s22s22p6

Ca:1s22s22p63s23p64s2

Ca2+:1s22s22p63s23p6

Zn:1s22s22p63s23p64s23d10

Zn2+:1s22s22p63s23p63d10