ATOMIC STRUCTURE S.MORRIS 2006

Timeline of Atomic Theory 450 BC 1800’s _________________________________________________________ Dalton: http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html http://www.fortbend.k12.tx.us/campuses/documents/Teacher/2009/teacher_20090928_0656_2.doc proposed 4 components to an Atomic Theory. Democritus: http://great-philosophers.suite101.com/article.cfm/democritus_and_atomistic_philosophy http://www.fortbend.k12.tx.us/campuses/documents/Teacher/2009/teacher_20090928_0656.doc matter was made of “atoms”

negative charge in the atom 1897 Atomic Theory 1897-1920 ___________________________________ Thomson http://highered.mcgraw-hill.com/sites/0072512644/student_view0/chapter2/animations_center.html negative charge in the atom 1897 Planck http://web2.uwindsor.ca/courses/physics/high_schools/2005/Photoelectric_effect/planck.html Quanta 1901 Millikan http://highered.mcgraw-hill.com/sites/0072512644/student_view0/chapter2/animations_center.html charge on e- 1910 Bohr http://www.wwnorton.com/college/chemistry/gilbert/tutorials/ch3.htm#top http://www.chempractice.com/drills/java_Bohr.php quantum model 1913 Rutherford http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf nucleus 1911

Contributions to Modern Atomic Theory De Broglie Wave nature of matter 1924 _____________________________________ Gell-Mann Quarks 1962 Heisenberg e- is a wave and a particle 1926 Schrodinger e- orbits as a wave 1926 Chadwick neutron 1932

(greek for indivisible) HISTORY OF THE ATOM Democritus develops the idea of atoms 460 BC 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)

HISTORY OF THE ATOM ATOMS John Dalton 1808 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

HISTORY OF THE ATOM ELECTRON Joseph John Thompson 1898 found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON

HISTORY OF THE ATOM PLUM PUDDING MODEL 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/chapter2/animations_center.html#

Planck and the Quanta Click to read about Planck and his experiments and ideas http://web2.uwindsor.ca/courses/physics/high_schools/2005/Photoelectric_effect/planck.html

Millikan 1910 http://highered.mcgraw-hill.com/sites/0072512644/student_view0/chapter2/animations_center.html Charge on an electron

HISTORY OF THE ATOM Ernest Rutherford: The Gold Foil Experiment 1910 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 However, this was not the end of the story. 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.

HISTORY OF THE ATOM Niels Bohr 1913 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 electrons in orbits nucleus

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

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= n0 = 3 quarks Electron Cloud Electrons =e- (particle/wave) Held together by a force called : Gluon

Quarks = up (+2/3) and down (-1/3) Gluon forces between quarks 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 n0 = 2 down and 1 up +2 +2 -1 = +1 -1 -1 +2 = 0 3 3 3 3 3 3 Gluon forces between quarks

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