Atomic TheoryHistory of the Discoveries Related to the Atom
Mr. Kendall
Main Contributors To Atomic Theory 450 BC 1800 1897 1901 1910 1911 1913
Democritus: Matter made of tiny things
called ATOMS
Dalton: Wrote an Atomic
Theory with 4 main ideas
Thompsonnegative charge in the atom
Planck: Quanta,
predictable packets of
energy
Millikan: Charge on
the electron of -1
Rutherford: atoms have a nucleus
Bohr: Proposed a model of an
atom
1924 1926 1926 1932 1962
Debroglie: Matter has a
wave-like nature
Schrödinger: E- travel in
waves
Heisenberg: E- are waves and particles
Chadwick: neutrons
Gell-Mann: Quarks
Timeline of Atomic Theory 450 BC 1800’s
_________________________________________________________
Democritus: http://www.fortbend.k12.tx.us/campuses/documents/Teacher/2008/teacher_20081003_1616.doc
matter was made of “atoms”
Dalton: http://www.iun.edu/~cpanhd/C101webnotes/composition/dalton.html
proposed 4 components to an
Atomic Theory.
Dalton’s Theory: Foundation of Future Investigations
• 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, whole-number ratio.
http://web.visionlearning.com/dalton_playhouse/ad_loader.html
Click the link at home to explore more about
experiments related to Dalton’s theory.
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://www.science.uwaterloo.ca/~cchieh/cact/c120/emwave.html
Quanta 1901
Rutherfordhttp://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/ruther14.swf
nucleus 1911
Bohr http://www.wwnorton.com/college/chemistry/gilbert/tutorials/ch3.htm#top
http://www.chempractice.com/drills/java_Bohr.php
quantum model 1913
Millikan http://highered.mcgraw-
hill.com/sites/0072512644/student_view0/chapter2/animations_center.html
charge on e-
1910
Contributions to Modern Atomic Theory
_____________________________________
De Broglie Wave
nature of matter
1924
Schrodinger e- orbits as a
wave 1926
Heisenberg e- is a wave
and a particle 1926
Chadwick neutron
1932
Gell-Mann Quarks
1962
3 Basic Parts of the Atom.
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
Electrons travel in waves
Electrons are Particles / Photons• Electrons travel in discreet packets called photons. • To describe these unique packets or quantities of
energy the term “quanta” is used. • Every element on the periodic table is made up of atoms
with a unique signature of spectral lines• http://phys.educ.ksu.edu/vqm/html/emission.html
Predicting the Location of an Electron in an Atom:
• Bohr proposed 4 characteristics to consider to predict the location of an electron.– l = the distance from the nucleus– m = the shape of the orbital in which the e-
occupies. (s,p,d,f)– n = axis the orbital occupies. (x, y, z)– s =spin of the e- (+1/2 , -1/2)
Distance from the nucleus:• Levels 1-7: When looking at the periodic
table, can be determined by the period number. Elementary Connections
12
34
56
7
Shape of the Orbital on the x,y,z Axis
• The number of electrons in a particular region determines the shape.
s shape 2e- p shape 6e-
Shape of the Orbital on the x,y,z Axis
d shape 10e- f shape 14e-
Atom with overlapping orbitals
Spin of the Electron• http://www.colorado.edu/physics/2000/applets/a2.html
Do Electrons behave as a particle or as wave?
Definition of Light:– http://chemmovies.unl.edu/
ChemAnime/DEFLITD/DEFLITD.html
Einstein vs BohrEinstein: causality Bohr: Predictability
If you know all the initial conditions of
your system and you know the laws of
physics, you can figure out exactly what’s going to happen
If you know the initial
conditions and you know the
laws of physics, you
can figure out the probability
of various outcomes
happening, but you can never know which
one will definitely
occur until after it’s over.
Electron behavior as it moves to other energy levels.
• This emitted energy is equal to the difference between the high and low energy levels, and may be seen as light.
Light emission tutorial http://www2.wwnorton.com/college/chemistry/gilbert/tutorials/ch3.htm
Electrons exhibit particle and wave like behavior
“Duality”
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