Download 3.2-3.3 Honors Notes - teacherstroh

Last Name:
First Name:
Period:
Unit 2: Atoms and the Periodic Table
Date:
History and Evolution of Atomic Theory NOTES
Key Point #1:_________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Key Point #2:_________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
ATOMIC THEORY TIMELINE
Democritus 460-370BC
PICTURE
Experiment:
Where/When:
Conclusions:
Are atoms divisible?
YES
NO
Question to ponder: Why was Democritus’ idea not a theory?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
John Dalton: 1766-1844
Experiment:
PICTURE
Where/When:
Conclusions:
Are atoms divisible?
YES
NO
Dalton’s Conclusions (page 52 in your book!)
1. Elements are made of tiny particles called atoms.
2. All atoms of a given element are identical.
3. The atoms of a given element are different from those of any other element.
4. Atoms of one element can combine with atoms of other elements to form compounds.
5. Atoms are indivisible in chemical processes. Atoms are not created or destroyed, just rearranged.
Questions to ponder: Why would people believe John Dalton and not Democritus? What makes John
Dalton’s ideas about the atom a theory and Democritus’ ideas a thought?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
J.J. Thompson: Late 1856-1940
Experiment:
PICTURE
Where/When:
Conclusions:
Are atoms divisible?
YES
NO
Question to ponder: If atoms are neutral and electrons are negative, what else could scientists infer about
the atom? How did Thomson’s experiment reject the idea that atoms are indivisible?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Lord Ernest Rutherford: 1871-1937
Experiment:
PICTURE
Where/When:
Conclusions:
Are atoms divisible?
YES
NO
You’re Rutherford: What are your conclusions?
__________________________________________
__________________________________________
__________________________________________
__________________________________________
__________________________________________
__________________________________________
__________________________________________
Niels Bohr: 1885-1962
Niels Bohr was a Danish physicist. He proposed a model of the atom that is similar to the model of the
solar system. The electrons go around the nucleus like planets orbit around the sun. All electrons have their
energy levels – a certain distance from the nucleus. Each energy level can hold a certain number of
electrons.
Vocabulary

Energy level:

Valence electron:
Question to ponder: Why could Bohr’s model be called the Solar System Model of the atom?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
Edwin Schrödinger: 1887-1961
What did Schrodinger think??? (Take notes on your own here!)
Unit Test Practice!
1) Who first thought that the atom was divisible? How did he figure it out?
2) Why did Rutherford’s alpha particles sometimes bounce back?
3) Why do you think the most common way people depict the atom is Niels Bohr’s model and not
Shrodinger’s (even though Shrodinger’s is newer)?
4) Pick two of the scientists in order of either of the two days. Explain how the later scientist adapted and
modified the previous scientist’s theory. Make sure you:
a. Describe both theories
b. Describe how the later scientist’s evidence disproved or modified the earlier scientist’s theory