Ion: Electron Configuration

Question

Write the complete electron configuration for the iron(III) ion.

Using NOBLE GAS notation write the electron configuration for the manganese(II) ion.

Answer 1

Looking at neutral iron (no charge), we have atomic number 26 and it is in period 4, group 8. It is a d-block transition metal and so the electron configuration is [Ar] 3d⁶ 4s². Now, to become Fe3+, it has to lose 3 electrons and those will be the outermost, so it will lose the 4s² and one electron from 3d. The resulting electron configuration for Fe(III) ion is [Ar]3d⁵

Mg²⁺ = magnesium(II). Neutral Mg has 12 electrons and is in period 3 group 2 and is an s-block element.

Neutral Mg looks like this: [Ne]3s². To become Mg²⁺, it must lose 2 electrons, and those will be the 3s electrons. The resulting electron configuration for Mg(II) ion is [Ne]