1. History of the Discoveries Related to the Atom Mrs. Paul
Atomic Theory
History of the Discoveries Related to the Atom
Mrs. Paul

2. Main Contributors To Atomic Theory
450 BC
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
Dalton: Wrote an Atomic Theory with 4 main ideas
Thompson
negative charge in the atom
Democritus: Matter made of tiny things called ATOMS
Chadwick: neutrons
Debroglie: Matter has a wave-like nature
Heisenberg: E- are waves and particles
Gell-Mann: Quarks
Schrödinger: E- travel in waves

3. Timeline of Atomic Theory
450 BC ’s
_________________________________________________________
Dalton:
proposed 4 components to an Atomic Theory.
Democritus:
matter was made of “atoms”

4. 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.
Click the picture to explore more about experiments related to Dalton’s theory.

5. Atomic Theory 1897-1962 Sub-Atomic Particles
___1897________ 1910________ 1911_________1913________1932________1962___
Thomson
Cathode Ray Experiment
Negative charge in the atom
Millikan
Oil Drop Experiment
Charge on e- is 1-
Rutherford
Gold Foil Experiment
Alpha Particles and Nucleus Animation
Nucleus
Bohr
Bohr Model
Bohr’s Discovery
Quantum Model
Chadwick
History of Chadwick
Neutron
Gell-Mann
What are p+ and n0?
Quarks

6. 3 Basic Parts of the Atom. Click on this link and participate in the interactive questions

7. Quarks = up (+2/3) and down (-1/3) Gluon forces between quarks
Types of Quarks Determine Charge
Quarks = up (+2/3) and down (-1/3)
p+ = 2ups and 1 down n0 = 2 down and 1 up
= = 0
Gluon forces between quarks

8. Energy Nature of Matter 1900-1926
____________1905______1924_____1926______1926__
1900
Planck
Quantum Hypothesis
Atoms Absorb and Emit Light
Photo Electric Animation
Quanta
Einstein
Matter and Energy different forms of the same thing
E=mc2 Explained
E=mc2
De Broglie Wave nature of matter
Heisenberg
Uncertainty
e- acts as a wave and a particle
Schrodinger
e- orbits as a wave

9. Are they a particle or a wave?
Electrons……..
Are they a particle or a wave?

10. Electrons travel in waves
Click this link for explanation

11. Electrons as Waves
Electrons travel in discreet packets called photons which travel in waves.
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. Click the picture below

12. 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.
Click the picture for animation

13. Electrons as a Particle having position in an Atom
Electrons are particles with a charge of 1- , it has mass, and its position can be predicted with reliability.
Bohr proposed 4 characteristics to predict the position 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)

14. 1. 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

15. 2. Shape of the Orbital 3. On the x,y,z Axis
The # of electrons in a particular region determines the shape.
s shape 2e p shape 6 e d shape 10 e-
f shape 14 e-

16. Atom with overlapping orbitals

17. 4. Spin of the Electron

18. Electrons exhibit particle and wave like behavior called “Duality”
Click here for animation

19. Einstein vs Bohr Bohr: Predictability Einstein: causality
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.
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

20. 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