Connect photoelectron peaks to electron structure

What does an electron-removal spectrum represent?

A photoelectron experiment connects an incoming photon, an atom or ion, and an emitted electron. A removal channel requiring more energy leaves less energy for the emitted electron when the photon energy is held fixed. This is an energy-accounting question before it is a graph-reading exercise.

The two packets in this widget are invented ideal gas-phase schematics. Their energies are teaching values, not measured sodium or magnesium spectra and not extracted from a NIST occupied-subshell dataset. They make an occupancy/energy argument inspectable while keeping the empirical limitation explicit. No instrument construction, ion-source operation or hazardous experiment is required.

A shell/subshell label describes an electronic state, not a circular path around the nucleus. If the notation is unfamiliar, use electron arrangements and return. The existing neutral H–Ar table is a reference model; it is not itself spectroscopic evidence.

Connect peak strengths to an occupancy ledger

Packet N has ideal peak strengths 2, 2, 6 and 1, assigned in order to 1s, 2s, 2p and 3s. Equal response and equal peak widths are part of the packet contract. Under that idealization the strengths correspond to electron counts, totaling 11. With separately stipulated neutral atomic number 11, the configuration is 1s² 2s² 2p⁶ 3s¹.

Packet M instead has strengths 2, 2, 6 and 2, totaling 12, with neutral atomic number 12 and configuration 1s² 2s² 2p⁶ 3s². The additional outer electron changes the occupancy ledger. Our assigned binding energies also change between packets. Explain the direction using increased nuclear attraction and shielding/shell context, but do not infer exact energies from proton count alone.

Core electrons generally experience different attraction and shielding than outer electrons. The packet’s inner 1s channel has much larger removal energy than its 3s channel. This does not mean that an electron has that positive energy while bound: the displayed number is an energy needed to remove it under the specified convention.

Real spectra do not universally obey “peak height equals electron count.” Different response factors, widths, overlap and final-state structure can alter signals. Here widths and response are stipulated equal so both height and integrated-strength comparisons support the same simple ratio. Do not transfer that inference to arbitrary measured peaks without checking the method.

Read the axes before comparing positions

Both widget energy axes increase from left to right and use the same fixed 0–1800 eV range. Other published PES graphs may run in the opposite direction. The table gives exact assigned values, especially where valence peaks sit close together on the full-range plot. A visual cluster does not mean the model assigned equal energies.

One plot shows binding energy; the other shows emitted kinetic energy. Under the declared ideal isolated gas-phase approximation, with a common vacuum reference and recoil omitted,

emitted kinetic energy = photon energy − binding energy.

For packet N at 1500 eV photon energy, its 1000 eV channel emits an electron with 500 eV kinetic energy. Its 5 eV channel gives 1495 eV. These are different outgoing channels, not one electron receiving the sum of all listed energies.

Increase the photon energy to 1800 eV. The same channels become 800 and 1795 eV, each 300 eV higher. The binding energies and occupancy are held fixed in this comparison. Capture both settings and check every row, not only the visually separated core peak. All offered photon energies exceed the largest assigned binding energy; this widget does not model thresholds or omitted inaccessible channels.

A solid-surface XPS analysis requires its energy references and instrument/work-function conventions. Do not apply this unqualified gas-phase equation to a surface measurement or interpret the omitted physics as zero in real instruments.

What the references support

The NIST WebBook gas-phase methods discussion explains the relevant measurement quantities and more complete energy accounts. The NIST ASD ionization-energy documentation distinguishes reported energies, units, uncertainty and references. A table of ground-state configurations and ionization energies is not a complete measured occupied-subshell PES packet. Neither source supplies the widget’s invented binding values.

The AP Chemistry course framework connects spectral representations with configurations and electron–nucleus interactions. This opening neutral-species comparison does not exhaust atom/ion configurations, periodic trends or all of Unit 1. Additional evidence and broader cases remain required in the course plan.

Apply to another original packet

A separately stipulated neutral species has occupied-subshell strengths 2, 2 and 5 in 1s, 2s and 2p. What electron total and configuration follow under equal response? One channel has binding energy 400 eV and the photons have energy 1200 eV. Predict the emitted kinetic energy, then explain what changes if photon energy rises to 1500 eV.

Check the new-packet reasoning

The total is 9 electrons and configuration 1s² 2s² 2p⁵. Under neutrality the proton count is 9; without neutrality, electron total alone would not determine the element. The emitted kinetic energy is initially 800 eV, then 1100 eV. Binding remains 400 eV in this stipulated comparison. If relative response were unknown, the raw strengths alone would not securely identify occupancy.

In your reflection, connect input photon energy, the removal channel and the outgoing electron. State both the useful inference and its model boundary. Return to the partial AP Chemistry course for the delivered sequence and remaining scope. Retaining these settings and explanations does not award a full project, supervised lab or independent mastery.