What is the noble gas electron configuration of an iron cation with a 3+ charge Fe3+?

  You need to write the

 electron configuration

 of Fe3+ using noble gas

 notation.

Remember that the atomic number of iron is 26.

Here is the electron configuration of Fe^3+ using noble gas notation:

[Ar]3d⁵

The noble gas argon is used here.The atomic number of argon is 18.

Remember that the d subshell has five orbitals.Each orbit can take maximum two electrons.

In case of filling degenerate orbits ,each orbital will take one electron before pairing by the second electron according to Hunds' rule.

The Fe^3+ ion has five unpaired electrons.That is why it is paramagnetic.

The Fe^3+ has 26 protons but 23 electrons.