A simplified PES trace for gaseous scandium (atomic number 21) shows the peaks listed…
CHEMISTRY · Multi-part · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
A simplified PES trace for gaseous scandium (atomic number 21) shows the peaks listed below.
Peak label
Binding energy / kJ mol⁻¹
Relative height
A
395
2
B
115
2
C
95
6
D
50
2
E
35
6
F
20
3
G
6
2
Use this information to analyze scandium’s electronic structure.
(a) Assign each peak (A–G) to a specific subshell and write the complete ground-state electron configuration of scandium.
(b) When scandium forms the ion Sc³⁺ in aqueous solution, which electrons are removed first? Use quantitative evidence from the PES data to justify your answer.
(c) Despite the order in which subshells are filled in the neutral atom, peak F (3d electrons) appears at a higher binding energy than peak G (4s electrons). Explain this apparent anomaly in terms of radial distribution and electron-electron repulsion.
(d) Using your explanation in part (c), account for the fact that the electron configuration of Sc³⁺ ends in 3p⁶ rather than 3d¹.