Chapter 01 · Unit 1: The Composition of Matter · Segment 1

Atoms and Elements

What are the smallest pieces of matter, how do we know they exist, and how do scientists keep track of the different kinds?

MS-PS1-1 · practiceMS-ETS1-1 · assesses Textbook pp. 8–19 1 presentation · 10 worksheets · 3 labs
Student bundle (no keys) (8.6 MB)Teacher bundle (password) (10.6 MB)

Overview

Students figure out that every bit of matter, including invisible air, is built from atoms that are far too small to see, and that fewer than a hundred kinds of atoms occur in nature. They learn how two physicists defined criteria and constraints to invent a microscope that maps surfaces atom by atom, and how chemists a century earlier found patterns in properties and atomic mass that grew into the periodic table. By the end they can read an element's symbol, mass and position on the table and use that position to predict how the element behaves. This chapter is the foundation for modeling molecules in Lesson 2 and for every chemistry lesson that follows.

Estimated class time: presentation about 142 minutes · worksheets about 375 minutes in total · labs 4 sessions. Six to seven 50-minute periods: two for the phenomenon, scale and the atom/element distinction; two for the STM engineering story and the touch-probe design lab; two for classification history, the periodic table and the mystery-card lab; one for synthesis and mastery.

Phenomenon

The balloon that gains mass from nothing you can see

A limp party balloon sits on a sensitive balance and reads 1.85 grams. A student pumps it full of air with a hand pump, ties it off, dries the outside, and puts it back. Now the balance reads 1.89 grams. (The readings are illustrative values, realistic for a small party balloon.) Nothing visible was added, yet the balloon is measurably heavier. If the stuff inside has mass, what is it made of, how small are its pieces, and why can we not see them?

Notice and wonder prompts

  • What exactly did the pump push into the balloon, and where did it come from?
  • If air has mass, why does a room full of it feel like nothing at all?
  • How small would the pieces of air have to be for billions of them to fit in one balloon?
  • Would a balloon filled from a helium tank gain mass too? More or less than one filled with air?

Learning targets

  • I can explain that all matter is made of atoms and tell the difference between an atom and an element.
  • I can compare the atomic scale to everyday scales and explain why atoms need their own unit, the picometer.
  • I can describe how a scanning tunneling microscope maps a surface and identify the criteria and constraints its inventors defined.
  • I can explain how patterns in properties and atomic mass led from element trios to the periodic table, and why blank spaces were a prediction.
  • I can use an element's symbol, atomic mass and position on the periodic table to predict some of its properties.

What shows the learning happened

  • A labeled scale ladder placing a meter, a millimeter, a sand grain, a bacterium and an atom in order with the correct unit for each, plus a one-sentence justification for why the picometer exists.
  • A completed halving graph (Lab 1) with a written estimate, including the reasoning, of how many halvings it would take to reach the width of one atom.
  • A predicted periodic arrangement of mystery element cards (Lab 2) with blank spaces justified by property patterns and an estimated atomic mass for one missing card.
  • A written set of criteria and constraints for a touch-probe mapping tool (Lab 3 or W9), each criterion measurable and each constraint tied to a real limit.
  • A Claim-Evidence-Reasoning paragraph (W6) arguing that air is matter made of particles, citing balloon-mass evidence.
  • A short answer that correctly distinguishes 'an atom of carbon' from 'the element carbon' and uses a chemical symbol correctly.

Key vocabulary 12 terms

matterAnything that has mass and takes up space. Solids, liquids and gases are matter; light and sound are not.The air inside the balloon is matter, so the balance reads a little higher once the balloon is full.
atomA single particle of an element, the smallest piece of a substance that still counts as that element.One atom of neon is far too small to see, but trillions of them together glow red inside a lit sign.
elementA substance made of only one kind of atom. Carbon, iron and neon are elements; water and air are not.Diamond and pencil graphite look nothing alike, yet both are the element carbon.
atomic scaleThe range of sizes where atoms live, roughly a hundred to a few hundred picometers across, far below what any eye or light microscope can show.A ruler marked in centimeters is useless on the atomic scale, so scientists switch to picometers.
picometer (pm)A unit of length equal to one trillionth of a meter, written 10⁻¹² m. Most atoms are about 100 to 300 pm wide.The STM had to tell apart features about 100 pm apart, otherwise neighboring atoms would blur into one bump.
criteriaThe requirements a design must satisfy for the solution to count as a success.One criterion for the new microscope was that it could show the position of single atoms on a surface.
constraintA limit on what solutions are possible, such as time, money, available technology or the physical conditions of the work.Vibration from people walking in the building was a constraint, so the team collected data at night.
scanning tunneling microscope (STM)An instrument that maps a surface atom by atom by moving an extremely sharp probe just above it and tracking a tiny electric current that grows when the probe is closer to the surface.An STM does not use light or lenses, so its map is built from current readings, not from an image a lens formed.
atomic massThe mass of an atom, measured in daltons. The value printed on the periodic table is an average for the element's atoms, which can differ slightly from one another.Oxygen's atomic mass of about 16 Da tells you one oxygen atom has about sixteen times the mass of one hydrogen atom.
periodic table of the elementsA chart of every known element arranged in rows and columns so that elements with similar properties line up in the same column.Because neon sits in the far-right column, a chemist expects it to be a gas that rarely reacts, like its column neighbors argon and krypton.
groupA column of the periodic table. Elements in a group tend to share properties and react in similar ways.Lithium, sodium and potassium are in the same group, and all three react with water.
chemical symbolA one- or two-letter shorthand for an element's name, used by scientists in every language. Some come from older names, such as Pb for lead from the Latin plumbum.A chemist in Japan and a chemist in Mexico both write Fe and both mean iron.

Standards alignment

California NGSS, Grade 7 Preferred Integrated Course Model. Each entry says whether this chapter's work assesses the performance expectation, gives practice toward it, or supports it as background; the resource lists below repeat this for every worksheet and lab.

MS-PS1-1Practice toward: the atoms-as-building-blocks foundation of PS1.A, before molecule models are builtCA Grade 7

Develop models to describe the atomic composition of simple molecules and extended structures.

This lesson establishes that substances are made of different kinds of atoms and introduces the periodic table as the catalog of those kinds. Students build and use models of atomic scale and of the table, which prepares them to model molecules and extended structures in Lesson 2; no slide or task here asks for a molecule model, so the role is practice, not assesses.

Assessment boundary: Assessment does not include valence electrons and bonding energy, discussing the ionic nature of subunits of complex structures, or a complete description of all individual atoms in a complex molecule or extended structure is not required.

MS-ETS1-1Assesses: defining criteria and constraints precisely for a tool-design problemCA Grade 6-8

Define the criteria and constraints of a design problem with sufficient precision to ensure a successful solution, taking into account relevant scientific principles and potential impacts on people and the natural environment that may limit possible solutions.

The lesson's engineering spread tells how Rohrer and Binnig stated what their microscope had to do and what limited them. Lab 3 and Worksheet 9 require students to write their own criteria and constraints for a probe-based mapping tool, with measurable precision, before designing, which is direct evidence toward this PE.

Science and engineering practices

  • Developing and Using Models. Students use a halving model (Lab 1), a periodic-arrangement model (Lab 2) and particle drawings to represent atoms and elements, and they treat the periodic table itself as a model that predicts properties.
  • Asking Questions and Defining Problems. Students define criteria and constraints for a touch-based mapping tool (Lab 3, W9) and compare their definitions with the ones the STM inventors used.
  • Analyzing and Interpreting Data. Students plot strip lengths against number of halvings (Lab 1) and use atomic-mass patterns in mystery element cards (Lab 2, W5) to find trends and predict missing values.

Disciplinary core ideas

  • PS1.A Structure and Properties of Matter. All matter is made of atoms; different elements are different kinds of atoms; elements combine in many ways to make the substances around us; the periodic table organizes elements by shared properties.
  • ETS1.A Defining and Delimiting Engineering Problems. The STM story and Lab 3 show that a design problem is more likely to be solved when its criteria and constraints are stated precisely, including the scientific facts that limit solutions.

Crosscutting concepts

  • Scale, Proportion, and Quantity. Students reason about how many halvings reach the picometer scale, why atoms need their own unit, and how 10¹⁹ atoms can sit in a sand grain.
  • Patterns. Students look for repeating patterns in properties and atomic mass, the same patterns that led to the periodic table, and use them to place mystery elements.
  • Influence of Science, Engineering, and Technology on Society and the Natural World. Students see how a new instrument (the STM) opened a view of the world that no earlier tool could give, and how a chart (the periodic table) became a shared language for chemists everywhere.

Presentation 28 slides

Atoms and Elements: the smallest pieces of matter. Original, editable slides with speaker notes: a phenomenon opener, learning targets, the chapter's concepts with diagrams, vocabulary in context, 4 checks for understanding, 2 discussion prompts, an application task, a misconception check, a synthesis and an exit ticket.

PowerPoint (editable)Slides PDFSpeaker notes PDFSpeaker notes (web)

Worksheets 10 of 10

Ten different tasks, one per instructional blueprint. Each has a student PDF (low ink, US Letter), an editable DOCX, an HTML preview, and a separate teacher answer key with reasoning.

Collaborative labs 3 of 3

Three different investigation approaches. Each has a teacher guide (purpose, materials with quantities, estimated cost, prep, safety, procedure, expected observations, debrief, answer key, assessment criteria, accessibility adaptations, low-cost alternative) and a student recording sheet.

First page of the The Mystery Element Cards: Build a Table That Predicts recording sheet
Lab 2 · Evidence-based mystery

The Mystery Element Cards: Build a Table That Predicts

Given only the properties and atomic masses of fourteen unnamed elements, can your group arrange them into a table that reveals a pattern, and can that table predict elements you were never given?

Groups of 41 session40 min activityEst. 3 to 5 per classMystery element card set (14 cards), printed on card stock and cut apartBlank index cards for gap predictionsLarge sheet of paper or a desk-sized whiteboard for laying out the grid MS-PS1-1 · practice
Recording sheet PDFRecording sheet DOCXPreview
Teacher only
Teacher guide PDFTeacher guide DOCXGuide preview
First page of the Design a Touch Microscope: Map a Surface You Cannot See recording sheet
Lab 3 · Engineering design challenge

Design a Touch Microscope: Map a Surface You Cannot See

What criteria and constraints must a probe-based mapping method meet to produce a trustworthy map of a hidden surface, and how does your method compare with a scanning tunneling microscope?

Groups of 42 sessions80 min activityEst. 12 to 20 per classShoebox with lidLandscape pieces: modeling clay, bottle caps, blocks, folded card, a small cupWhite glue or double-sided tape to fix pieces to the box floor MS-ETS1-1 · assessesMS-PS1-1 · supports
Recording sheet PDFRecording sheet DOCXPreview
Teacher only
Teacher guide PDFTeacher guide DOCXGuide preview

Teacher guidance

Suggested sequence (7 steps)
  1. Period 1: Presentation slides 1-8 (phenomenon, targets, matter and particles, atom vs. element). W1 phenomenon worksheet as the opener, W2 vocabulary relationships as the exit activity.
  2. Period 2: Lab 1, the halving investigation of scale (one session). Students plot strip length against halvings and estimate the halvings needed to reach one atom. Follow with slides 9-11 on the scale ladder and the picometer.
  3. Period 3: Slides 12-17 (engineering problem, criteria vs. constraints, how the STM maps a surface, the San Jose connection). W3 reading passage for homework or in class. W4 diagram interpretation of an STM scan.
  4. Period 4: Lab 3, the shoebox touch-microscope design challenge, session 1 (define criteria and constraints, design the probe method). W9 transfer task can replace the lab's design brief if time is short.
  5. Period 5: Lab 3 session 2 (map the hidden surface, compare the map to the real surface, revise). Slides 18-21 (trios, classification timeline, Mendeleev's blanks, the blank-space discussion) and W7 misconception repair.
  6. Period 6: Lab 2, the mystery element cards (one session). Slides 22-25 (table neighborhoods, reading a tile, the mystery-element task with simulated data, position check). W5 data worksheet and W8 collaborative sorting share the same card logic and can follow.
  7. Period 7: Slides 26-28 (misconception, synthesis, exit). W6 CER on the balloon evidence as the written assessment, then W10 mastery as the quiz.

Materials overview: No chemicals and no open flames anywhere in the chapter. Lab 1 uses paper strips, rulers and graph paper. Lab 2 uses printed mystery element cards. Lab 3 uses shoeboxes, cardboard, modeling clay or glued-on objects, bamboo skewers and grid paper. A digital balance reading to 0.01 g and a hand pump make the balloon phenomenon a live demonstration; otherwise describe it with the numbers in the phenomenon text.

Common misconceptions (5)
“Air and other gases are not matter, or have no mass.”
Why it happens: Students cannot see, hold or weigh air with their senses, and everyday language calls an air-filled container empty.
Correction: Air is a mixture of gas particles, mostly nitrogen and oxygen molecules, each with mass. A balloon filled with compressed air reads measurably heavier on a balance, and a tire gets heavier when inflated.
“An element and an atom are the same thing.”
Why it happens: The textbook's vocabulary box calls an element a particle, and classroom shorthand often says 'carbon is an atom.'
Correction: An atom is a single particle. An element is a substance made of only that kind of atom. A diamond is the element carbon; it is made of a vast number of carbon atoms.
“If we keep cutting something in half, we can go on forever; there is no smallest piece.”
Why it happens: Every cut students have ever made produced two pieces that could be cut again, so the pattern seems endless.
Correction: Matter is grainy at the bottom. After roughly 30 to 40 halvings of an everyday object you reach single atoms, and splitting an atom no longer gives you smaller pieces of the same element.
“Microscopes like the STM take a photograph of atoms with light.”
Why it happens: The word microscope and the look of STM images suggest a camera.
Correction: An STM has no lenses. It drags a sharp probe just above the surface and records a tiny current that grows when the probe is nearer to the surface. A computer turns those readings into a map, so the image is reconstructed data, not a photograph.
“Every atom of an element has exactly the same mass, and the periodic table is simply sorted by mass.”
Why it happens: The textbook says all atoms of an element share one atomic mass and describes the table as ordered by increasing mass.
Correction: Most elements come in a few varieties (isotopes) that differ slightly in mass, so the printed value is an average. The modern table is ordered by atomic number, which is why argon (39.9 Da) comes before potassium (39.1 Da).
Differentiation suggestions (5)
  • Multilingual learners: Pre-teach the five anchor terms (matter, atom, element, criteria, constraint) with a picture-and-gesture card set; let students label the scale ladder in their home language first and then in English; pair during Lab 2 so that card properties are read aloud.
  • Students who need more support: Provide the halving data table in Lab 1 with the first four rows filled in, a word bank for the criteria/constraints sort, and a sentence frame for the CER ('The balloon gained ___ g, which shows ___ because ___').
  • Students ready for extension: Ask them to explain why argon sits before potassium even though its atomic mass is larger, to research the 1955 field ion microscope and compare its limits with the STM's, or to estimate how many atoms lie along the width of a human hair.
  • Students who need movement or alternative output: Run the scale ladder as a floor line across the room with students holding unit cards; allow the Lab 3 map to be presented as a physical clay model instead of a drawing; let the synthesis be recorded as a 60-second spoken explanation.
  • Students with limited fine-motor control or low vision: Use wide strips of card instead of paper in Lab 1 and stop at eight halvings; provide large-print mystery cards with raised-dot markers for reactivity; let a partner operate the probe in Lab 3 while the student calls the grid positions and interprets the map.
Accuracy notes: where the textbook simplifies (13)
  • Natural element count: the textbook says 92 elements occur naturally (pp. 9, 10, 16). The count depends on convention: trace plutonium in uranium ore pushes it to 94 by some reckonings, while technetium and promethium occur only as fleeting traces from uranium fission. Teach 'fewer than a hundred' or 'about 90' and never assess an exact number.
  • Element versus atom: the textbook's vocabulary box (p. 9) calls an element a unique particle. Use the Key Science Concept definition (p. 16): an element is a substance made of only one kind of atom; an atom is one particle of it.
  • Atomic mass: the book says every atom of an element has one identical mass (pp. 9, 14). Most elements are mixtures of isotopes, so the tabulated value is a weighted average and individual atoms differ a little. Keep daltons as the unit; say 'about 1 Da' for hydrogen (actual average 1.008).
  • Ordering of the table: the book describes the table as ordered by increasing atomic mass with 'a few exceptions' (p. 18). The modern table is ordered by atomic number (the number of protons), which students meet later; argon/potassium and tellurium/iodine are the visible exceptions. Mendeleev himself placed tellurium before iodine on the strength of their properties.
  • The STM and 'seeing atoms first': the book says the STM proved atoms exist and let people see them for the first time (pp. 13, 19). Atoms were firmly established by the early 1900s, and the field ion microscope imaged individual atoms on sharp metal tips in 1955. Say instead that the STM, working by 1981, was the first tool that could map an ordinary flat surface atom by atom. Binnig and Rohrer shared the 1986 Nobel Prize in Physics (with Ernst Ruska, for the electron microscope).
  • How the STM works: at this level say that a tiny current flows between the probe and the surface when they are extremely close, and that the current grows sharply as the gap shrinks. Do not describe the current as 'detecting the shape of atoms' by touch; the probe never touches. In practice most STMs move the probe up and down to keep the current constant and record the probe height; the constant-height picture used in the deck is the simpler teaching version.
  • Picometer: 1 pm is 10⁻¹² m, so a meter holds one trillion picometers. The OCR of the book garbles the exponent. Typical atoms are roughly 100 to 300 pm across; the STM criterion of about 100 pm resolution is the book's figure and is reasonable.
  • Grand Canyon comparison (p. 11): 5 × 10¹⁹ ping-pong balls would fill a box the size of the canyon only a few hundred times (about 400 if the balls were packed solid, roughly 600 allowing for the gaps between balls; W9's extension walks the arithmetic), not 500,000. The deck keeps the sand-grain count as a rough estimate and drops the canyon comparison.
  • Classification history: Johann Wolfgang Döbereiner published his element trios in 1829 (he noticed the first one around 1817); John Newlands proposed his repeating-eights pattern in 1864-1865 and was mocked for it before being honored later; Dmitri Mendeleev published his first table in 1869 and the version with predictions for gallium, scandium and germanium in 1871. Julius Lothar Meyer built a similar table at the same time; the book omits him. The book's 'Greg Binnig' caption (p. 12) should read Gerd Binnig.
  • Alkali metals and water: the book's Figure 5 caption says lithium, sodium and potassium all burn on contact with water, but its own text (p. 14) says lithium only fizzes. Lithium reacts steadily without igniting; sodium reacts fast enough that it can ignite; potassium ignites at once. Never demonstrate; describe only.
  • Chemical symbols: say one or two letters. Three-letter symbols are temporary placeholders for unnamed new elements; the four the book's Figure 5 still shows (Uut, Uup, Uus, Uuo) were replaced by Nh, Mc, Ts and Og in 2016.
  • Balloon phenomenon: a balloon filled by a pump reads heavier because the air inside is squeezed to a higher pressure than the air outside, so it is denser than the air the balloon pushes aside. A balloon at the same pressure as the room would read almost the same as when empty. Keep this buoyancy detail for your own understanding unless a student asks.
  • 'Everything is made of atoms' (pp. 10, 16): all matter is made of atoms. Light and sound are not matter, so say 'all matter' rather than 'everything'.

Review status: reviewed · 2026-10-18 · Re-solved every numeric and multiple-choice item in W1-W10 and Labs 1-3 (68 keyed items plus the slide checks); all keys agreed with independent solutions except as noted below. Lab 2: corrected the claim that all three gaps fall in one row (bromine's gap is in the potassium/krypton row; rubidium and strontium's gaps are in the iodine/xenon row) and fixed a row/column mix-up in likelyDifficulties. Presentation: Newlands' medal came from the Royal Society (Davy Medal, 1887), not the Chemical Society; light-microscope limit restated as a few hundred nanometers rather than 'the size of a bacterium'; halving count for a 10 cm nail corrected to about 30; the slide-24 task now says its names and masses are the Lab 2 cards rounded, to be used after the lab. Grand Canyon accuracy note made consistent with the W9 extension arithmetic (about 400-600 canyon-fulls). Balloon phenomenon readings labeled as illustrative values in the chapter and the slide notes. W10 q6 switched from the Cl/Br/I triad (already the computation in W5 q8 and W8 q2) to the Ca/Sr/Ba triad so the quiz is not a third repeat. Originality sweep: four short phrases shared with the lesson text reworded (W3 passage, W7 key, W9 extension, W10 key, Lab 2 debrief, two teacher accuracy notes); remaining matches are section titles in sourceReferences. W4 grid diagram converted from 'categories' to 'items' with labels, the field the authoring guide specifies for grid. Lab cost bases now say they are estimates; Lab 2 safety line reworded so it does not overstate classroom practice. Not changed, flagged for authors: W8 (jigsaw) and Lab 2 (mystery cards) share the same core reasoning (sort cards into behavior columns, find a hole, average to predict bromine); they differ in format and card count but a student doing both will repeat the exercise.

Source references

Verified against the student edition of Bring Science Alive! 7th Grade Integrated (Student Edition). Printed page numbers appear in the book; PDF pages are the physical pages of the 524-page scan (printed + 36). The textbook is not reproduced on this site.

SectionPrinted pagesPDF pagesUsed for
Introduction: the neon tube that looks empty8, 944, 45Lesson question, the 'empty' tube idea, vocabulary list, standards listed by the publisher.
1. Atoms: halving a nail, the sand-grain count, scale and the picometer10, 1146, 47Lab 1 halving model, scale-ladder diagram, the atom/element distinction, slide content on scale.
2. Engineering Tools to Observe Atoms: criteria, constraints and the STM12, 1348, 49Engineering story, criteria vs. constraints compare diagram, STM flow diagram, Lab 3 design challenge.
3. Classifying Elements: Döbereiner's trios and atomic mass1450Trio pattern, dalton unit, the averaging idea used in Lab 2 and W5.
4. The Periodic Table: Newlands, Mendeleev and the blank spaces1551Timeline diagram, the prediction of gallium, scandium and germanium, Lab 2 blank-space reasoning.
Key Science Concept: The Periodic Table of Elements16, 1752, 53The clearer element definition, element masses and symbols used for table-reading tasks.
5. Using the Periodic Table: groups, periods, symbols18, 1954, 55Group and period patterns, noble gases and alkali metals, chemical-symbol origins, lesson summary.

External references used for accuracy checks

Related chapters

Ch. 2: Molecules and Extended StructuresCh. 3: Substances and Their PropertiesCh. 13: Atoms in Chemical ReactionsCh. 23: The Motion of Particles
Next chapter →Chapter 2: Molecules and Extended Structures