Atomic Patterns Worksheet
NGSS MS-PS1-1 • Physical Science
Atomic Patterns: Molecules vs. Extended Structures
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Date: Period:
Part 1: Science Reader — Two Ways Atoms Build Matter
All matter is built from tiny particles called atoms. When atoms chemically bond, they organize into one of two fundamental arrangements: molecules or extended structures.
1. Molecules
A molecule is a standalone, independent cluster of atoms bonded in a fixed number and ratio. For example, a water molecule (H2O) has exactly two hydrogens and one oxygen. It is a discrete unit that does not continue into a repeating grid.
2. Extended Structures
An extended structure is an interconnected network or lattice of bonded atoms repeating in all directions with no fixed ending. In table salt (NaCl), sodium and chlorine alternate throughout a continuous 3D pattern. The formula shows the ratio (1:1), not a lone pair.
Simple Model: Water Molecule (H2O)
O H H
Standalone discrete unit (3 total atoms, closed edges)
Extended Structure: Salt Lattice (NaCl)
Na Cl Na Cl Cl Na Cl Na Na Cl Na Cl
3-row repeating lattice extending in all directions (•••)
Part 2: Identify and Count Atoms
Carefully observe each model before answering.
Model A O C O Carbon Dioxide (CO2)
1. Count of Carbon (C) atoms:
2. Count of Oxygen (O) atoms:
3. Structure Type:
Molecule Extended
4. How do you know?
Model B Si O Si O Si O Si O Si Silicon & Oxygen Network
1. Silicon (Si) atoms in this view:
2. Oxygen (O) atoms in this view:
3. Structure Type:
Molecule Extended
4. Visual clue that indicates this:
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MS-PS1-1 Practice Investigating Patterns & Review
Student Name:
Part 3: Decoding Patterns in an Extended Structure
Repeating Multi-Row Model of an Unknown Mineral Crystal Segment
X Y X Y X Y X Y X Y X Y X Y X Y X Y X Y X
Dashed bonds (•••) indicate the atomic pattern repeats continuously in all directions (horizontal & vertical).
1. What two different types of atoms are present in this model?
2. Look at the top row. If the pattern continues to the right, which atom would come next?
3. Explain the rule or pattern you used to make your prediction in question 2:
4. How do you know this model represents an extended structure rather than a molecule?
Part 4: Comprehensive Model Review
Count atoms, identify repeating patterns, and classify.
Model 1: Ammonia (NH3)
N H H H
Atom Counts:
N: H:
Repeats in all directions?
Yes No
Classification:
Model 2: Zinc & Sulfur
Zn S Zn S Zn S Zn S Zn
Visible Counts:
Zn: S:
Repeats in all directions?
Yes No
Classification:
Model 3: Oxygen Gas (O2)
O O
Atom Counts:
O: (Total: )
Repeats in all directions?
Yes No
Classification:
5. Final Synthesis: In your own words, what is the single biggest visual difference between a model of a molecule and a model of an extended structure?
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