Atomic Theory History of the Discoveries Related to the Atom

Timeline of Atomic Theory 450 BC 1800’s _________________________________________________________ Democritus: Teacher/2008/teacher_ _1616.doc matter was made of “atoms” Dalton: mposition/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. ml Click the link at home to explore more about experiments related to Dalton’s theory.

Atomic Theory ___________________________________ Thomson hill.com/sites/ /student_vi ew0/chapter2/animations_center.htm l negative charge in the atom 1897 Planck ourses/physics/high_sch ools/2005/Photoelectric_e ffect/planck.html Quanta 1901 Rutherford sci/chemistry/essentialche mistry/flash/ruther14.swf nucleus 1911 Bohr emistry/gilbert/tutorials/ch3.htm#top ava_Bohr.php quantum model 1913 Millikan hill.com/sites/ /stude nt_view0/chapter2/animations_c enter.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= n 0 = 3 quarks Electron Cloud –Electrons =e- (particle/wave) Held together by a force called : Gluon

Types of Quarks Determine Charge Quarks = up (+2/3) and down (-1/3) p+ = 2ups and 1 down n 0 = 2 down and 1 up = = 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

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

Do Electrons behave as a particle or as wave? Definition of Light: – hemAnime/DEFLITD/DEFLIT D.htmlhttp://chemmovies.unl.edu/C hemAnime/DEFLITD/DEFLIT D.html

Einstein vs Bohr Einstein: causalityBohr: 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 orials/ch3.htm orials/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”