Question

name: date: q2 chemistry: u3l9 pes day 1 prepwork part 2: pes spectra of 2 elements directions: read the passage below. as you read, annotate the important information and vocabulary words. then answer the questions. part 1: read & annotate: sometimes, scientists compare two pes graphs on the same plot to analyze and identify unknown elements. these graphs might look similar in shape (same number of peaks), but differences in binding energy and number of protons or zeff help us figure out which graph belongs to which element. key ideas for comparison 1. binding energy and zeff o elements with more protons (higher atomic number) exert a greater nuclear pull - on electron. o according to coulombs law, greater zeff means stronger attraction & higher binding energy. o on a pes graph, this means that all peaks shift closer to the nucleus (higher binding energy) for the element with more protons or higher zeff. 2. peak count and electron configuration: o the number of distinct peaks tells you how many occupied sublevels the atom has. o the height of each peak reflects how many electrons are in each sublevel. example: comparing li and be lets say you see two pes graphs: • graph of li has two peaks at: o 1s→6.26 mj/mol (2 electrons) o 2s→0.52 mj/mol (1 electron) • graph of be has two peaks at: o 1s→11.5 mj/mol (2 electrons) o 2s→0.90 mj/mol (2 electrons) both graphs show: • two peaks→two sublevels (1s and 2s) • same pattern→first peak (1s) is taller (2 electrons). but graph of be has higher binding energy for both peaks. this tells you that be has higher zeff and greater number of protons. conclusion: • graph a = li (z = 3)→1s²2s¹ • graph b = be (z = 4)→1s²2s² even though theyre similar in structure, the higher binding energies in graph b reveal that they belong to the atom with greater nuclear charge. part 2: multiple choice 1. if two pes graphs have the same number of peaks, but one has all peaks at higher binding energies, which statement is most likely true? a. both atoms have the same number of protons b. the one with higher binding energy has more electrons c. the one with higher binding energy has more protons d. the peaks dont relate to atomic structure 2. *what does a taller peak mean in a pes spectrum? a. greater binding energy b. more electrons in that sublevel c. stronger coulombic attraction d. a full energy level

Explanation:

For question 1:

• Option A: Different binding energies imply different Zeff (related to proton number), so not same proton number.
• Option B: Binding energy is more related to proton number (nuclear charge) than total electron count (as seen in Li and Be example where Be has higher binding energy with more protons but not just more electrons in a general sense compared to all elements).
• Option C: As per the text, higher binding energy (due to stronger nuclear pull - more protons or higher Zeff) is the key.
• Option D: Peaks relate to atomic structure (sublevels, electron count in sublevels, binding energy related to proton number).

For question 2:

• Option A: Taller peak is about electron count in sublevel, not binding energy (binding energy is x - axis related).
• Option B: The text clearly states “The height of each peak reflects how many electrons are in each sublevel”.
• Option C: Stronger Coulombic attraction is related to binding energy (x - axis), not peak height.
• Option D: A full energy level is not indicated by peak height (peak count is for sublevels, height for electron count in sublevel).

Answer:

1. C. The one with higher binding energy has more protons
2. B. More electrons in that sublevel