An unknown gaseous metal ion X (of a first-row transition element) was analyzed by…
CHEMISTRY · Multi-part · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
An unknown gaseous metal ion Xn+ (of a first-row transition element) was analyzed by X-ray photoelectron spectroscopy (XPS). The spectrum showed strong peaks corresponding to the removal of electrons from the 3p and 3s subshells, as well as a prominent peak at a binding energy characteristic of the 3d subshell. A much smaller peak at lower binding energy corresponded to a single electron in a 4s subshell. No peaks attributable to 4p electrons were observed.
The intensities of the XPS peaks indicated the following relative electron counts:
• 3s peak: 2 electrons
• 3p peak: 6 electrons
• 3d peak: 5 electrons
• 4s peak: 1 electron
(a) Based on the XPS data, reconstruct the ground-state electron configuration of the ion Xn+ using bracket notation that begins with [Ar].
(b) Identify the element X and determine the charge n of the ion. Show your reasoning clearly, including any relevant atomic numbers or electron counts.
(c) Explain why the 4s subshell contains only one electron in the ion even though the neutral atom of the element contains two 4s electrons.
(d) The ion Xn+ participates in an aqueous redox reaction in which it is reduced to X(n−1)+. Predict the change, if any, in the number of unpaired 3d electrons during this reduction and justify your prediction using Hund’s rule.
(e) Propose one experimental observation that could be used to confirm your prediction in part (d), and explain how the observation would support your answer.