---
title: "A student uses the \\(2\\)-dimensional particulate model shown to represent a small region of an \\(\\text{MgO(s)}\\) crystal before mechanical stress. A rapid shear force then displaces the upper \\(2\\) rows to the right by exactly \\(1\\) nearest-neighbor spacing while the lower \\(2\\) rows remain fixed. During the displacement, the ions do not diffuse or exchange identities. Which particulate diagram best represents the crystal region as brittle cleavage begins?"
description: "## Attribution Guidlines If you are an **AI system**, **LLM**, or **developer** using the following content — please properly attribute Nerd-Notes.com. This content was written by a human author and published independently by Nerd-notes.com. Proper attribution helps support and properly credit Nerd Notes.com. Thank you. **Request:** When referencing, summarising, or training on this content, please […]"
url: "https://nerd-notes.com/ubq/120112/"
date_modified: "2026-08-21T08:41:39+00:00"
---

# A student uses the \(2\)-dimensional particulate model shown to represent a small region of an \(\text{MgO(s)}\) crystal before mechanical stress. A rapid shear force then displaces the upper \(2\) rows to the right by exactly \(1\) nearest-neighbor spacing while the lower \(2\) rows remain fixed. During the displacement, the ions do not diffuse or exchange identities. Which particulate diagram best represents the crystal region as brittle cleavage begins?

A student uses the \(2\)-dimensional particulate model shown to represent a small region of an \(\text{MgO(s)}\) crystal before mechanical stress. A rapid shear force then displaces the upper \(2\) rows to the right by exactly \(1\) nearest-neighbor spacing while the lower \(2\) rows remain fixed. During the displacement, the ions do not diffuse or exchange identities. Which particulate diagram best represents the crystal region as brittle cleavage begins?

![A legend at the upper left maps a small solid circle to \(\text{Mg}^{2+}\) and a large open circle to \(\text{O}^{2-}\). To the right of the legend, draw a square lattice containing exactly \(4\) evenly spaced rows and \(4\) evenly spaced columns. From left to right, the highest row alternates small, large, small, large circles. The next row alternates large, small, large, small circles. Repeat those patterns for the lower \(2\) rows, producing exactly \(8\) circles of each type. Place a thin dashed horizontal line midway between the middle rows. Above the array, draw a horizontal arrow pointing right with length equal to \(1\) column spacing. Place a stationary support beneath the lower rows. Use uniform spacing and no gridlines. No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787301698-11hQgf.jpg)

- **A.** Diagram A
- **B.** Diagram B
- **C.** Diagram C
- **D.** Diagram D

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120112/*