Atomic TheoryHistory of the Discoveries Related to the Atom

Timeline of Atomic Theory 450 BC 1800’s

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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 5 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://web2.uwindsor.ca/courses/physics/high_schools/2005/Photoelectric_effect/planck.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.

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

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

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.

Electrons travel in waves

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 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

Electrons exhibit particle and wave like behavior

“Duality”