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The Structure of the Atom Honors Chemistry Section 3.2
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Honors Chemistry Section 3.2

Jan 01, 2016

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Honors Chemistry Section 3.2. The Structure of the Atom. The Think Tube. Demonstrate the Think Tube. Atom. The smallest particle of an element that still retains the properties of that element. Made of two regions Nucleus In center of atom Extremely small Majority of Mass of Atom - PowerPoint PPT Presentation
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Page 1: Honors Chemistry Section 3.2

The Structure of the Atom

Honors ChemistrySection 3.2

Page 2: Honors Chemistry Section 3.2

Demonstrate the Think Tube

The Think Tube

Page 3: Honors Chemistry Section 3.2

The smallest particle of an element that still retains the properties of that element.

Made of two regionsNucleus

In center of atomExtremely smallMajority of Mass of AtomProtons/Neutrons

Electron CloudContains electrons

Atom

Page 4: Honors Chemistry Section 3.2

The Atom

Page 5: Honors Chemistry Section 3.2

Parts of the Atom

Video

Page 6: Honors Chemistry Section 3.2

Properties of Subatomic Particles

Page 7: Honors Chemistry Section 3.2

How did we find the electron?J.J. Thomson – late 1800’sUse the Cathode Ray Tube

Page 8: Honors Chemistry Section 3.2

Thomson's Experiment

Page 9: Honors Chemistry Section 3.2

Thompson's Experiment

Video

Page 10: Honors Chemistry Section 3.2

Cathode Rays move away from a negative charge

Cathode Rays move away from a magnetic field in the same manner as a wire carrying a negative charge

Found the Cathode Rays have mass – could move a paddle wheel in their path

Charge to mass ratio of Cathode Rays the same regardless ofType of metal used in electrodesType of gas used in tube

Thomson's Observations

Page 11: Honors Chemistry Section 3.2

Cathode Rays are negatively chargedCathode Rays must be a fundamental particle

of matterCalculated the charge to mass ratio of the

particlesParticles later named electrons

Thomson's Conculsions

Page 12: Honors Chemistry Section 3.2

Robert Millikan

Page 13: Honors Chemistry Section 3.2

Millikan's Experiment

Video

Page 14: Honors Chemistry Section 3.2

Determined the fundamental charge on matter (the electron)

Used Thomson’s charge to mass ratio to determine the mass of an electron

Verified that electrons are negative

Millikan's Results

Page 15: Honors Chemistry Section 3.2

Atom is divisibleOne of the basic subatomic particles is the

negatively charged electronAtom is electrically neutral, so it must contain

positive charges to balance out the electronsElectrons have an extremely small mass,

therefore there must be other massive particles in the atom

Results

Page 16: Honors Chemistry Section 3.2

Thomson's and Millikan's Model

Page 17: Honors Chemistry Section 3.2

Demo the Cloud Chamber

Radiation Demonstration

Page 18: Honors Chemistry Section 3.2

Ernest Rutherford - 1911

α particles are positively charged and massiveHe nucleus

Page 19: Honors Chemistry Section 3.2

Rutherford's Results

Page 20: Honors Chemistry Section 3.2

Rutherford's Experiment

Video

Page 21: Honors Chemistry Section 3.2

Nucleus existed at the center of the atomSmall – extremely smallMassiveDensely PackedPositive

Electrons are in orbit around the nucleus.

Rutherford's Conclusions

Page 22: Honors Chemistry Section 3.2

All nuclei (execpt H) have protons and neutrons

Proton – positiveCharge equal and opposite the electronMass about the same as a neutron1.673 x 10-27 kg (1836 x the mass of an

electron)Neutron – electrically neutral

1.675 x 10-27 kgAtom neutral so # protons = # electronsThe number of protons determines the

identity of the element

Early 1900's Atomic Theory

Page 23: Honors Chemistry Section 3.2

When two protons are extremely close to each other, there is a strong attraction between them.

A similar attraction exists when neutrons are very close to each other or when protons and neutrons are very close together.

The short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together are referred to as nuclear forces.

Forces in the Nucleus

Page 24: Honors Chemistry Section 3.2

Nuclear Forces

Page 25: Honors Chemistry Section 3.2

• The radius of an atom is the distance from the center of the nucleus to the outer portion of its electron cloud.

• Because atomic radii are so small, they are expressed using a unit that is more convenient for the sizes of atoms.

• This unit is the picometer, pm.

The Size of an Atom