The photoelectron spectrum of a neutral iron atom shows a strong peak near 700 kJ mol…
CHEMISTRY · Single correct · AP · Chemistry · Atomic Structure and Properties · Atomic Structure and Properties
Problem
The photoelectron spectrum of a neutral iron atom shows a strong peak near 700 kJ mol−1 attributed to 3d electrons and a smaller peak near 400 kJ mol−1 attributed to 4s electrons. Which statement most plausibly accounts for the higher binding energy of the 3d electrons even though the 4s subshell is filled first during electron configuration writing?
(a) 4s electrons experience a larger effective nuclear charge than 3d electrons because they are the outermost electrons; therefore they should require more energy to remove.
(b) The Aufbau principle is incorrect; the spectrum shows that the 3d subshell actually fills before the 4s subshell in a neutral iron atom.
(c) 3d electrons experience a larger effective nuclear charge than 4s electrons because they shield one another poorly, resulting in stronger attraction to the nucleus.
(d) 3d orbitals are more diffuse than 4s orbitals, placing their electrons farther from the nucleus and therefore binding them more strongly.