Atomic theory
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Atomic Theory. History of the Discoveries Related to the Atom Mr. Addison. Timeline of Atomic Theory. 450 BC 1800’s _________________________________________________________. Democritus: matter was made of “atoms”.

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Atomic Theory

History of the Discoveries Related to the Atom

Mr. Addison


Timeline of Atomic Theory

450 BC 1800’s

_________________________________________________________

Democritus:

matter was made of “atoms”

Dalton:

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.

  • Elements are characterized by the mass of their atoms.

  • When elements react, their atoms combine in simple, whole-number ratios.

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


Atomic Theory 1897-1920

___________________________________

Planck quanta 1901

Bohr quantum model 1913

Rutherford nucleus 1911

Thompson negative charge in the atom 1897


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


Experiments that Characterized Particles of the Atom

  • Thompson Cathode Ray tube:

    • Electrons are negative in charge

    • http://chemmovies.unl.edu/ChemAnime/CATHRAYD/CATHRAYD.html

  • Rutherford’s Gold Foil:

    • Nucleus contains protons and is very small/dense

    • http://www2.wwnorton.com/college/chemistry/gilbert/tutorials/ch3.htm

  • Bohr model:

    • Electrons travel in certain paths

    • http://chemmovies.unl.edu/ChemAnime/BOHRQD/BOHRQD.html


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

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

p+ = 2ups and 1 downn0 = 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.

1

2

3

4

5

6

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 and Bohr

Bohr:

-Predictability

Einstein:

-causality


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”


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