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4.2

Lesson 4.2 Structure of the Nuclear Atom

Objectives

● 4.2.1 Identify three types of subatomic particles.

● 4.2.2 Describe the structure of atoms according to theRutherford atomic model.

Lesson Links

Ch. 4 Lab 5: Atomic Structure: Rutherford’s Experiment

Ch. 4 Core TR: Section 2 Review

4.2 Lesson Overview (PowerPoint file)

4.2 Kinetic Art: Rutherford's Experiment

4.2 Kinetic Art: Cathode Ray

Chapter 4 Online Student Edition

Ch. 4 Directed Virtual Lab: Rutherford's Experiment

Overview/Materials

Overview

In this lesson you will cover the three types of subatomic particles:electrons, protons, and neutrons. You will also cover the experimentsused to determine the structure of the atom and its nucleus.

Classroom Materials

Subatomic Particles: cathode-ray tube, magnet

The Atomic Nucleus: Library or Internet access

Quick Lab: box containing a regularly shaped object fixed in place, and aloose marble

Differentiated Instruction: balloons, swatches of wool cloth

Pacing

Standard

1.5

Block

0.75

Standard

There are no items.

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Chemistry & You

Description

Engage

Have students study the Chemistry & Youfeature on p. 105.

Ask How could you determine what yourhand looks like under the skin withoutdissecting it? (X-rays, CT scans, or MRIscans) Explain that scientists usetechnology to "see" inside atoms, just asdoctors use it to "see" inside the body.

Resources

Content Chapter 4 Online StudentEdition

Pacing

Build Background

Description

Engage

Ask Do you have an electronic item in yourhome that uses a CRT? (Sample answers: atelevision or computer monitor) Explain thattelevision and computer CRTs have asource of rays at the small end. The raysare projected on the large receiving end tocreate the display.

Resources Pacing

Subatomic Particles

Description

Explore

Use a quick teacher demonstration todemonstrate a cathode-ray tube andobserve properties of cathode rays.

Use a magnet to deflect the beam ofparticles in a cathode-ray tube. Review thecomponents of a cathode-ray tube, anddiscuss the connection to television picturetubes and computer monitors. Studentsshould be able to explain how the CRTworks and see how the cathode ray isdeflected by the magnetic field.

Materials: cathode-ray tube, magnet

Have students complete the 4.2 Kinetic Art:Cathode Ray on PearsonChem.com.

Resources

Content 4.2 Kinetic Art: CathodeRay

Pacing

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Subatomic Particles

Description

Explain

Have students study Table 4.1 and comparethe masses and charges of the threeelementary particles. Students shouldrecognize from this comparison that themass of an atom is due mainly to thenumber of protons and neutrons that it has.Point out that the assigned charges forprotons and electrons are relative charges.

Ask What particles make up most of themass of an atom? (protons and neutrons)

Ask Why are relative charges and massuseful in talking about subatomic particles? (The actual values are unwieldy numbers.)The absolute charge on an electron is 1.602177 × 10–19 coulombs.

Resources

Content Table 4.1

Pacing

The Atomic Nucleus

Description

Explore

Use the following activity to trace the historyof atomic models and examine the role ofthe scientific method in the development ofsuch models.

Have students create a timeline that tracesthe development of the atomic model. Havethem note the data that led to an existingmodel being changed. Students' timelinesshould list at least some of the atomicmodels shown on p. 133. Students shouldbe able to explain how certain scientificdiscoveries (e.g., Rutherford's gold foilexperiment) resulted in the revision of theprevailing atomic model at the time.

Materials: Library or Internet access

Have students complete the 4.2 Kinetic Art:Rutherford's Experiment on PearsonChem.com.

Resources

Content Chapter 4 Online StudentEdition

Pacing

The Atomic Nucleus

Description

Extend

Resources Pacing

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Explain to students that by 1887, the Britishscientist William Crookes knew that metalatoms contained negatively chargedparticles. He used a cathode ray tubecontaining hydrogen gas at low pressure,and discovered that hydrogen containspositive charges. Ask students to researchthe following: What conclusion about themass of the atom and the mass of itsprotons was derived from Crookes's findings? (The mass of an atom is greater than itsproton content.) Which subatomic particleaccounted for this additional mass? (theneutron)

The Atomic Nucleus

Description

Explain

Explain to students that the ratio of the sizeof the nucleus to the size of an atom isabout 10–5. Discuss how small the nucleusis compared to the entire atom. Explain thatif a housefly sitting on second base in abaseball stadium represented the nucleus ofan atom, the rest of the atom would be thesize of the stadium.

Resources Pacing

Quick Lab

Description

Purpose

The students will determine the shape of thehidden object by analyzing the reboundpaths of a marble rolled at the object.

Materials: box containing a regularlyshaped object fixed in place and a loosemarble

Prep Time

5 minutes

Class Time

10 minutes

Expected Outcome

Students' inferences may or may not bedifferent for the same object.

Resources Pacing

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For Enrichment

Make a more challenging black box forstudents who have an easy time with thesimple boxes. Put two single objects in onebox, or a single object with a complexshape.

Assess and Remediate

Description

Evaluate

Have each student come to your desk andorally state in one minute or less one of thediscoveries by Thomson, Millikan, orRutherford. Then ask them to describe howthe discovery led to the currentunderstanding of atomic structure.

Then, have students complete the 4.2Lesson Check.

Remediate

Have students review Table 4.1. Ask themto create a table or diagram to compare thecharacteristics of electrons, protons, andneutrons.

Resources

Content Chapter 4 Online StudentEdition

Pacing

Differentiated Instruction

Description

Less Proficient Readers

Direct Students to use Figure 4.4, Figure 4.5_part1 and Figure 4.5_part2 to describe J.J. Thomson's experiment with cathode-raytubes in their own words.

Special Students

Prior to explaining subatomic particles,divide students into small groups. Giveeach group a pair of inflated rubberballoons (be aware of any latex allergies inthe class) and a swatch of wool cloth. Havestudents rub the balloons vigorously with thewool. Have students test the balloonsagainst different objects and against eachother to discover how opposite chargesattract and like charges repel. Use thisactivity as a lead-in to Thomson's cathode-ray experiment.

Resources

Content Figure 4.4

Pacing

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Advanced Students

Have students use the Internet or library tofind the original papers for the discoveriesdescribed in this chapter and write a reporton what they have learned.

Focus on ELL

Description

Content and LanguageWrite the term subatomic on the board.Explain that the prefix sub- means "below"or "a part of." Have students brainstormthe literal meaning of subatomic. (belowatomic) Now write the words electron,proton, and neutron on the board. Explainthat in these three words, the suffix -onmeans "subatomic particle."

Resources

Content Study WB Chapter 4Lesson 2

Pacing

My Notes

Homework