---
title: "A complete photoelectron spectrum of a neutral unknown element is shown below.  Based on the spectrum, which of the following correctly identifies the element and the total number of valence electrons in an atom of the element?"
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date_modified: "2026-09-28T11:59:58+00:00"
---

# A complete photoelectron spectrum of a neutral unknown element is shown below.

Based on the spectrum, which of the following correctly identifies the element and the total number of valence electrons in an atom of the element?

A complete photoelectron spectrum of a neutral unknown element is shown below.

Based on the spectrum, which of the following correctly identifies the element and the total number of valence electrons in an atom of the element?

![A grayscale photoelectron spectrum graph with a horizontal axis labeled Binding Energy (\(\text{MJ/mol}\)) and a vertical axis labeled Relative Number of Electrons. The horizontal axis is ordered from high binding energy on the left to low on the right, with logarithmic scale markers at \(1000\), \(100\), \(10\), \(1\), and \(0.1\). The vertical axis has uniform tick marks from \(0\) to \(8\) without gridlines. Exactly five solid black vertical peaks appear: peak 1 at \(208\text{ MJ/mol}\) with a height of \(2\) units; peak 2 at \(18.7\text{ MJ/mol}\) with a height of \(2\) units; peak 3 at \(13.5\text{ MJ/mol}\) with a height of \(6\) units; peak 4 at \(1.95\text{ MJ/mol}\) with a height of \(2\) units; and peak 5 at \(1.01\text{ MJ/mol}\) with a height of \(3\) units. No other peaks, labels, gridlines, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596797-JtMmnj.jpg)

- **A.** \(\text{Al}\), with \(3\) valence electrons, because the single peak at \(1.01\text{ MJ/mol}\) represents all electrons in the valence shell.
- **B.** \(\text{Si}\), with \(4\) valence electrons, because the rightmost peak corresponds to \(2\) electrons in the \(3p\) subshell.
- **C.** \(\text{N}\), with \(5\) valence electrons, because there are \(5\) distinct subshell peaks in the spectrum.
- **D.** \(\text{P}\), with \(5\) valence electrons, because the two peaks at the lowest binding energies correspond to electrons in the \(n = 3\) shell.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123501/*