CHEMISTRY · Multi-part · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
The noble gas argon (Ar), the alkali metal potassium (K), and the alkaline-earth metal calcium (Ca) are consecutive elements in Period 4 of the periodic table. Their ground-state electron configurations are given below.
Ar 1s² 2s² 2p⁶ 3s² 3p⁶
K 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹
Ca 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
A researcher records separate PES spectra for gaseous samples of these three elements using the same experimental conditions.
(a) Sketch a qualitative PES spectrum for argon, labeling each peak with its subshell and showing relative peak heights.
(b) On the same set of axes, add the spectrum you would expect for potassium. Clearly indicate any new peak(s) and any shifts in the positions of the pre-existing peaks relative to argon.
(c) Extend your sketch to include calcium. Indicate how the spectrum differs from that of potassium in both peak count and peak heights, and comment on any additional shifts in binding energy.
(d) Using the spectra you constructed, explain how the first-ionization energies of Ar, K, and Ca are reflected in the appearance and relative binding energies of the outermost-electron peaks.