---
title: "An isolated atom has four discrete energy levels: \\(E_1 = -12\\text{ eV}\\), \\(E_2 = -6\\text{ eV}\\), \\(E_3 = -3\\text{ eV}\\), and \\(E_4 = -1\\text{ eV}\\). Four possible single-step transitions between these levels are represented by labeled vertical arrows: Arrow 1 (from \\(E_1\\) to \\(E_4\\)), Arrow 2 (from \\(E_4\\) to \\(E_1\\)), Arrow 3 (from \\(E_2\\) to \\(E_1\\)), and Arrow 4 (from \\(E_1\\) to \\(E_2\\)). Which arrow represents a transition in which the atom emits a photon with the greatest momentum?"
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url: "https://nerd-notes.com/ubq/123511/"
date_modified: "2026-09-28T11:59:59+00:00"
---

# An isolated atom has four discrete energy levels: \(E_1 = -12\text{ eV}\), \(E_2 = -6\text{ eV}\), \(E_3 = -3\text{ eV}\), and \(E_4 = -1\text{ eV}\). Four possible single-step transitions between these levels are represented by labeled vertical arrows: Arrow 1 (from \(E_1\) to \(E_4\)), Arrow 2 (from \(E_4\) to \(E_1\)), Arrow 3 (from \(E_2\) to \(E_1\)), and Arrow 4 (from \(E_1\) to \(E_2\)). Which arrow represents a transition in which the atom emits a photon with the greatest momentum?

An isolated atom has four discrete energy levels: \(E_1 = -12\text{ eV}\), \(E_2 = -6\text{ eV}\), \(E_3 = -3\text{ eV}\), and \(E_4 = -1\text{ eV}\). Four possible single-step transitions between these levels are represented by labeled vertical arrows: Arrow 1 (from \(E_1\) to \(E_4\)), Arrow 2 (from \(E_4\) to \(E_1\)), Arrow 3 (from \(E_2\) to \(E_1\)), and Arrow 4 (from \(E_1\) to \(E_2\)). Which arrow represents a transition in which the atom emits a photon with the greatest momentum?

![An energy-level diagram consisting of four horizontal line segments stacked vertically. A vertical axis on the left is labeled E in electron-volts. From bottom to top, the horizontal lines are labeled E_1 = -12\text{ eV}, E_2 = -6\text{ eV}, E_3 = -3\text{ eV}, and E_4 = -1\text{ eV}. The vertical spacing between lines reflects the energy differences. Four vertical arrows appear between levels. Arrow 1 starts at the E_1 level and points upward to the E_4 level, labeled 1. Arrow 2 starts at the E_4 level and points downward to the E_1 level, labeled 2. Arrow 3 starts at the E_2 level and points downward to the E_1 level, labeled 3. Arrow 4 starts at the E_1 level and points upward to the E_2 level, labeled 4. No other labels, lines, text, or axes appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596799-evRdRE.jpg)

- **A.** Arrow 1
- **B.** Arrow 2
- **C.** Arrow 3
- **D.** Arrow 4

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123511/*