---
title: "The complete photoelectron spectrum for a pure sample of neutral magnesium, \\(\\text{Mg}\\), in the gas phase is shown below.  Which of the following statements correctly identifies a peak in the spectrum and provides a valid justification based on atomic structure?"
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url: "https://nerd-notes.com/ubq/119986/"
date_modified: "2026-08-21T08:31:38+00:00"
---

# The complete photoelectron spectrum for a pure sample of neutral magnesium, \(\text{Mg}\), in the gas phase is shown below.

Which of the following statements correctly identifies a peak in the spectrum and provides a valid justification based on atomic structure?

The complete photoelectron spectrum for a pure sample of neutral magnesium, \(\text{Mg}\), in the gas phase is shown below.

Which of the following statements correctly identifies a peak in the spectrum and provides a valid justification based on atomic structure?

![A grayscale photoelectron spectrum displayed on bare axes with no gridlines. The horizontal axis is labeled Binding Energy (MJ/mol) with values decreasing from left to right: 100, 10, 1.0, 0.1. The vertical axis is labeled Relative Number of Electrons. Four discrete, solid vertical peaks are positioned along the axis. From left to right: Peak 1 is located at approximately 126 MJ/mol with a relative height of 2 units; Peak 2 is located at approximately 9.0 MJ/mol with a relative height of 2 units; Peak 3 is located at approximately 5.3 MJ/mol with a relative height of 6 units (three times the height of Peak 2); Peak 4 is located at approximately 0.74 MJ/mol with a relative height of 2 units. Each peak is labeled above with Peak 1, Peak 2, Peak 3, and Peak 4, respectively. No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787301097-vyZlY9.jpg)

- **A.** Peak \(1\) corresponds to the \(3s\) subshell because valence electrons experience the greatest effective nuclear charge and have the highest binding energy.
- **B.** Peak \(3\) corresponds to the \(2p\) subshell because its relative height is three times that of Peak \(2\), which corresponds to the two electrons in the \(2s\) subshell.
- **C.** Peak \(3\) corresponds to the \(3p\) subshell because higher-energy valence subshells always hold a greater number of electrons than core subshells.
- **D.** Peak \(4\) corresponds to the \(1s\) subshell because core electrons are shielded by valence electrons and therefore have the lowest binding energy.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119986/*