The neutral atom of element Q and its +2 cation (Q²⁺) are analyzed separately by…
CHEMISTRY · Multi-part · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
The neutral atom of element Q and its +2 cation (Q²⁺) are analyzed separately by photoelectron spectroscopy under identical experimental conditions. The following qualitative statements describe the resulting spectra:
• For neutral Q, a prominent valence peak appears at 0.62 MJ mol⁻¹ (height = 2 electrons). Core peaks appear at 3.5 MJ mol⁻¹ (height = 2 electrons) and 17 MJ mol⁻¹ (height = 6 electrons).
• For Q²⁺, the same three peak groupings are present, but all peaks shift toward higher binding energy, and the valence peak height decreases.
Address the tasks below.
(a) Explain, on the basis of electrostatic interactions, why all peaks for Q²⁺ are observed at higher binding energy than those for neutral Q.
(b) Quantitatively predict the new approximate binding energy of the valence peak for Q²⁺ if the shift is known to be 0.30 MJ mol⁻¹ for electrons in that subshell. Show your calculation.
(c) The height of the valence peak for Q²⁺ corresponds to only 0 electrons on the vertical scale. Explain what this observation reveals about the electronic structure of Q²⁺ compared with neutral Q.
(d) Based on your answers above, discuss how formation of the Q²⁺ ion is expected to affect the chemical reactivity of the species relative to neutral Q.