Electron Configuration — Ions
Enter atomic number Z (1–118) and the ion’s charge (e.g., +2 for Fe2+, -1 for Cl−). Rules used: aufbau, Pauli exclusion, Hund’s rule; for d-block cations remove ns before \((n-1)d\).
Electron Configuration of Ions
General Chemistry • Electrons in Atoms
Frequently Asked Questions
How do you find the number of electrons in an ion from Z and charge?
Use E = Z - q, where q is the signed ionic charge. A + charge reduces electrons, while a - charge increases electrons.
Why are 4s electrons removed before 3d for transition-metal cations?
After the neutral atom is formed, the ns electrons are typically the outermost and are removed first during ionization. This is why d-block cations lose ns electrons before removing electrons from the (n-1)d subshell.
How is an anion electron configuration determined?
For anions, electrons are added to the neutral-atom configuration by continuing the aufbau filling order and applying Hund’s rule within partially filled subshells.
What is meant by the valence set for an ion?
The valence set is the group of outer electrons used for bonding and properties, which depends on whether the ion is main-group (highest n s and p), d-block cation (highest occupied d after ns removal), or f-block (occupied f and sometimes adjacent d).