S.MORRIS 2006

Timeline of Atomic Theory

450 BC 1800’s ________________________________________________________ _ Democritus: http://great philosophers.suite101.com/article.cfm/democritus_and_at omistic_philosophy http://www.fortbend.k12.tx.us/campuses/documents/Teach er/2009/teacher_20090928_0656.doc

matter was made of “atoms” Dalton: http://www.iun.edu/~cpanhd/C101webnotes/co mposition/dalton.html

http://www.fortbend.k12.tx.us/campuses/docu ments/Teacher/2009/teacher_20090928_0656_ 2.doc

proposed 4 components to an Atomic Theory.

Atomic Theory 1897-1920

___________________________________

Thomson http://highered.mcgraw hill.com/sites/0072512644/student_vi ew0/chapter2/animations_center.htm

l Planck http://web2.uwindsor.ca/c ourses/physics/high_sch ools/2005/Photoelectric_e ffect/planck.html

negative charge in the atom 1897 Quanta 1901 Millikan http://highered.mcgraw hill.com/sites/0072512644/stude nt_view0/chapter2/animations_c enter.html

charge on e 1910 Rutherford http://www.mhhe.com/phys sci/chemistry/essentialche mistry/flash/ruther14.swf

nucleus 1911 Bohr http://www.wwnorton.com/college/ch emistry/gilbert/tutorials/ch3.htm#top http://www.chempractice.com/drills/j ava_Bohr.php

quantum model 1913

Contributions to Modern Atomic Theory

De Broglie Wave nature of Heisenberg Gell-Mann Quarks

___________________________________

and a particle 1926 Schrodinger e- orbits as a wave 1926 Chadwick neutron 1932

HISTORY OF THE ATOM 460 BC

Democritus develops the idea of atoms he pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called

ATOMA

(greek for indivisible)

1808 HISTORY OF THE ATOM

John Dalton suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them

ATOMS

Dalton’s Atomic Theory

• • • •

All matter consists of tiny particles.

Atoms are indestructible and unchangeable (Has been modified with recent discoveries in nuclear chemistry) Elements are characterized by the mass of their atoms.

When elements react, their atoms combine in simple, whole-number ratios. Their atoms sometimes combine in more than one simple

Laws that came from Dalton’s Atomic Theory

• Law of Conservation of Mass (mass cannot be created or destroyed) • Law of Definite Composition/ Law of Proportions • Law of Multiple Proportions

1898 HISTORY OF THE ATOM

Joseph John Thompson found that atoms could sometimes eject a far smaller negative particle which he called an

ELECTRON

HISTORY OF THE ATOM 1904

Thomson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge like plums surrounded by pudding.

PLUM PUDDING MODEL

Thomson’s Experiment with the Cathode Ray Tube

http://highered.mcgraw hill.com/sites/0072512644/student_view0/c hapter2/animations_center.html#

Planck and the Quanta

• Click to read about Planck and his experiments and ideas •

http://web2.uwindsor.ca/courses/physics/hi gh_schools/2005/Photoelectric_effect/plan ck.html

Millikan 1910 •

http://highered.mcgraw hill.com/sites/0072512644/student_view 0/chapter2/animations_center.html

•

Charge on an electron

1910 HISTORY OF THE ATOM

Ernest Rutherford: The Gold Foil Experiment oversaw Geiger and Marsden carrying out his famous experiment. they fired Helium nuclei at a piece of gold foil which was only a few atoms thick.

they found that although most of them passed through. About 1 in 10,000 hit

HISTORY OF THE ATOM gold foil helium nuclei helium nuclei

They found that while most of the helium nuclei passed through the foil, a small number were deflected and, to their surprise, some helium nuclei bounced straight back. This indicated a small dense positively charged center.

HISTORY OF THE ATOM

Rutherford’s new evidence allowed him to propose a more detailed model with a

central nucleus

. He suggested that the

positive charge

was all in a central nucleus. With this holding the electrons in place by electrical attraction. The electrons occupied most of the space of an atom/ makes up most of the volume of an atom.

However, this was not the end of the story.

1913 HISTORY OF THE ATOM

Niels Bohr studied under Rutherford at the Victoria University in Manchester. Bohr refined Rutherford's idea by adding that the electrons were in

orbits

. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.

Bohr’s Atom nucleus electrons in orbits

HELIUM ATOM proton Shell + N N + electron What do these particles consist of?

neutron

More Practice with Bohr Model

http://www.chempractice.com/drills/java _Bohr.php

Parts of the atom

Particles of the Atom to date:

• •

Nucleus

–

Protons = p+ = 3 quarks

–

Neutrons= n Electron Cloud 0 = 3 quarks Held together by a force called : Gluon

–

Electrons =e- (particle/wave)

Types of Quarks Determine Charge

http://nobelprize.org/educational_games/physics/matter/1.html

Quarks = up (+2/3) and down (-1/3)

p+ = 2ups and 1 down up n 0 = 2 down and 1 +2 +2 -1 = +1 -1 -1 +2 = 0 3 3 3 3 3 3

Gluon forces between quarks

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