---
title: "A student examines idealized, equal-volume microscopic regions of two iron alloys. The atomic radii and relative atomic masses used in the models are shown in the table.  | Atom | Atomic radius (pm) | Relative atomic mass | |——|——————–|———————-| | \\(\\text{Fe}\\) | 126 | 55.8 | | \\(\\text{C}\\) | 70 | 12.0 | | \\(\\text{Ni}\\) | 124 | 58.7 |  Each particle shown represents one atom, and each rectangular region has the same volume and depth. Based on the representations and the data, which statement correctly identifies the two alloy types and compares their densities and expected malleabilities?"
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url: "https://nerd-notes.com/ubq/119465/"
date_modified: "2026-08-19T12:40:34+00:00"
---

# A student examines idealized, equal-volume microscopic regions of two iron alloys. The atomic radii and relative atomic masses used in the models are shown in the table.

| Atom | Atomic radius (pm) | Relative atomic mass |
|——|——————–|———————-|
| \(\text{Fe}\) | 126 | 55.8 |
| \(\text{C}\) | 70 | 12.0 |
| \(\text{Ni}\) | 124 | 58.7 |

Each particle shown represents one atom, and each rectangular region has the same volume and depth. Based on the representations and the data, which statement correctly identifies the two alloy types and compares their densities and expected malleabilities?

A student examines idealized, equal-volume microscopic regions of two iron alloys. The atomic radii and relative atomic masses used in the models are shown in the table.

| Atom | Atomic radius (pm) | Relative atomic mass |
|------|--------------------|----------------------|
| \(\text{Fe}\) | 126 | 55.8 |
| \(\text{C}\) | 70 | 12.0 |
| \(\text{Ni}\) | 124 | 58.7 |

Each particle shown represents one atom, and each rectangular region has the same volume and depth. Based on the representations and the data, which statement correctly identifies the two alloy types and compares their densities and expected malleabilities?

![A legend maps a large open circle to \(\text{Fe}\), a small solid-black circle to \(\text{C}\), and a large gray circle to \(\text{Ni}\). Draw two equal-size rectangular panels side by side. Panel I contains exactly nine large open circles arranged as three aligned horizontal rows of three, forming four square gaps. Place exactly four small solid-black circles, one at the center of each gap. Panel II contains a three-by-three array occupying the same relative positions as the open-circle array in the first panel. The top-center and bottom-right positions contain large gray circles; the other seven positions contain large open circles. All particles remain separate and do not overlap. No other particles, labels, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1787143234-D37f39.jpg)

- **A.** Alloy I is interstitial, and alloy II is substitutional. The alloys have the same density because each has nine atoms at lattice positions; alloy II is more malleable.
- **B.** Alloy I is interstitial, and alloy II is substitutional. Alloy I is denser because its four added carbon atoms contribute more mass than the two nickel substitutions add; alloy II is more malleable because its similarly sized atoms distort the lattice less.
- **C.** Alloy I is substitutional, and alloy II is interstitial. Alloy I is denser, and alloy II is more malleable; the alloy type is determined by which sample contains more solute atoms.
- **D.** Alloy I is interstitial, and alloy II is substitutional. Alloy I is denser and more malleable because the smaller carbon atoms fit into gaps without interfering with the sliding of iron-atom layers.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/119465/*