Mr. Chapman
Models & History of the Atom
Models of the Atom
A Historical Perspective
Early Greek Theories
Chemistry 20
400 B.C. – Democritus thought matter _____________________________________
_____________________. This led to the idea of _____________________________.
350 B.C. – Aristotle modified an earlier theory that ___________________________
_______________________________________________. Aristotle was _________.
However, his theory persisted for _________ years.
1800 – John __________ proposed a modern atomic model based on
_______________________________________________. Dalton’s theory proposed the following things, some of which were amazing accurate:
1.
All matter is made of atoms.
2.
Atoms of an element are _____________.
3.
Each _____________ has different _____________.
4.
Atoms of different ______________ combine in constant _________ to form compounds.
5.
Atoms are ______________________________________.
John Dalton’s ideas account for the Law of ____________________ of _________, and the Law of
______________ ______________________.

Mr. Chapman
Models & History of the Atom
Adding Electrons to the Model
Chemistry 20
Materials, when rubbed, can develop a ___________ difference. This electricity is called “__________ ________” when passed through an evacuated tube.
These rays have a small _________ and are _____________.
Thompson noted that these _______________ subatomic particles were a fundamental part of _______ atoms.
1) Dalton’s “Billiard ball” model (1800 – 1900):
_________________________________________________________
2) Thompson “Plum pudding” model (1900):
1)
2)
_________________________________________________________
3) The Rutherford Model (around 1910):
_________________________________________________________
3)
_________________________________________________________. http://www.youtube.com/watch?v=FfY4R5mkMY8
Ernest Rutherford
Rutherford shot _________ (  ) particles at gold foil.

Mr. Chapman
Models & History of the Atom
Bohr’s Model
Chemistry 20
 Electrons orbit the nucleus in ______________.
 Electrons can be bumped up to a ___________ shell if hit by an ____________ or a
_____________ of light.
The key point of Bohr’s model is that it shows negatively charged electrons orbiting the nucleus of an atom, and that each specific level has an energy associated with it.
Quantum Mechanical Model
• A _____________ of energy is the amount of energy required to move an electron from one energy level to another.
• The energy levels are like the _________ of a ladder but are not equally spaced.
• Energy levels are like the _______________ in Bohr’s atomic model.
• The model was developed in the 1920’s.
• Werner Heisenberg (Uncertainty Principle)
At any time, we cannot know exactly where an ___________ is ____________.
• Louis de Broglie (electron has wave properties)
Although they are _____________, electrons also act like ___________

Mr. Chapman
Models & History of the Atom
Chemistry 20
• Erwin Schrodinger (mathematical equations using probability, quantum numbers)
Summing up the Quantum Mechanical Model
1.
2.
3.