---
title: "The complete photoelectron spectra of two neutral, second-period elements, X and Y, are shown below.  Which of the following correctly identifies Element Y and explains why its \\(\\text{1s}\\) peak is located at a higher binding energy than the \\(\\text{1s}\\) peak of Element X?"
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url: "https://nerd-notes.com/ubq/119172/"
date_modified: "2026-08-19T12:32:47+00:00"
---

# The complete photoelectron spectra of two neutral, second-period elements, X and Y, are shown below.

Which of the following correctly identifies Element Y and explains why its \(\text{1s}\) peak is located at a higher binding energy than the \(\text{1s}\) peak of Element X?

The complete photoelectron spectra of two neutral, second-period elements, X and Y, are shown below.

Which of the following correctly identifies Element Y and explains why its \(\text{1s}\) peak is located at a higher binding energy than the \(\text{1s}\) peak of Element X?

![A 2D line plot representing two overlaid photoelectron spectra on a Cartesian plane with light gray gridlines. The horizontal axis is labeled "Binding Energy (MJ/mol)" and ranges from 60 on the left to 0 on the right. The vertical axis is labeled "Relative Number of Electrons" and ranges from 0 to 5. A legend indicates that a solid line represents Element X and a dashed line represents Element Y.

The spectrum for Element X (solid line) consists of three sharp vertical peaks:
- First peak at 39.6 MJ/mol with a height of 2.0 units
- Second peak at 2.45 MJ/mol with a height of 2.0 units
- Third peak at 1.40 MJ/mol with a height of 3.0 units

The spectrum for Element Y (dashed line) consists of three sharp vertical peaks:
- First peak at 52.6 MJ/mol with a height of 2.0 units
- Second peak at 3.04 MJ/mol with a height of 2.0 units
- Third peak at 1.31 MJ/mol with a height of 4.0 units

No other curves, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787142767-KYUG1e.jpg)

- **A.** Element Y is \(\text{C}\); its \(\text{1s}\) electrons experience less shielding from valence electrons, causing them to be held more tightly by the nucleus.
- **B.** Element Y is \(\text{O}\); its \(\text{1s}\) electrons experience greater electron-electron repulsion within the core subshell, which increases their binding energy.
- **C.** Element Y is \(\text{O}\); its nucleus contains a greater number of protons, exerting a stronger coulombic attraction on the core electrons.
- **D.** Element Y is \(\text{N}\); its \(\text{2p}\) subshell is exactly half-filled, which provides extra stability that shifts all binding energy peaks to higher values.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119172/*