Final answer:
The correct electron configuration for the chromium(III) ion using noble gas notation is [Ar]3d^3. However, choice d) [Ar]4s^23d^3 incorrectly includes the 4s electrons, which are not present in the Cr^3+ ion.
Step-by-step explanation:
To write the electron configuration for the chromium(III) ion using noble gas notation, you must first understand the electron configuration of neutral chromium. Chromium's electron configuration is an exception to the expected order. For the neutral chromium atom, it is [Ar]3d54s1. However, when chromium loses three electrons to form Cr3+, it loses the electrons from the 4s orbital first and then one from the 3d orbital. This results in the electron configuration [Ar]3d3 for the Cr3+ ion. So, the correct answer using the given choices would be option d) [Ar]4s23d3, although to represent chromium(III) ion accurately, the 4s electrons should not be included, thus it should be simply [Ar]3d3. This question illustrates the electron configuration of elements and ions, particularly transition metals, which often exhibit exceptions due to electron-electron interactions and stability of half-filled or fully filled d subshells.