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Chemistry CPS: Project #2: GUIDELINES
The History of the Atom:
 NAMES OF THE
SCIENTISTS:__________________________________________________
_____________________________________________________________
 Date assigned: ______________________________
 Date due: __________________________________
 Points: 50 points total: 30 points for the research worksheet & 20 points
for group presentation.
 Purpose: To research one of the three groups of great scientists and their
work in the contribution on the development of the modern view of the atom in
the world of chemistry.
 Objectives:
I.
Do an Internet search, obtain key information, and also highly
consider important facts:
1) Search the chemist via www.google.com
2) Find out about the scientist’s research:
 Scientific Discovery (laws, formulas, or theories)
II.
Complete the worksheet based on the research.
Scientists:
I. Atomic Structure-1:
1) Democritus(Atomos)
2) Aristotle(4 Key Elements of Nature)
3) John Dalton(5 Postulates on the Atomic Theory)
II. Atomic Structure-2:
4) John Joseph Thomson aka JJ Thomson(Cathode Ray Tube Experiment &
Plum Pudding Model)
5) Robert A. Millikan(Oil Drop Experiment)
6) Ernest Rutherford(Gold Foil Bombardment Experiment)
7) James Chadwick(Neutrons)
8) Niels Bohr(Planetary Model)
III. Periodic Table:
9) Stanislao Cannizzaro(standard atomic masses)
10) Dmitri Mendeleev aka Mendeleyev(increasing atomic masses)
11) Henry Moseley(increasing atomic numbers)
12) Glen Seaborg(Transition and Inner-Transition Metals)
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Chemistry CPS: Project #2: WORKSHEET
The History of the Atom:
 NAMES OF THE
SCIENTISTS:__________________________________________________
_____________________________________________________________
 Date assigned: ______________________________
 Date due: __________________________________
Answer all 30 questions correctly for credit.
I. Atomic Structure-1:
1) How did Democritus explain the composition(make-up) of matter?
2) What does atomos mean?
3) How did Aristotle explain the composition(make-up) of matter?
4) What are the four Key Elements of Nature?
5) What is the significance of his four components of matter? What doe they
represent?
6) How did John Dalton explain the composition(make-up) of matter?
7) Who does John Dalton agree with Democritus or Aristotle? Why?
Explain.
8) What are the five Postulates on the Atomic Theory?
9) Which three fundamental laws arise from his Atomic Theory? Explain
each of the three laws.
10) Which of his five postulates on Atomic Theory are now incorrect?
Explain.
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II.
Atomic Structure-2:
11) What did J.J. Thomson discover in his Cathode Ray Tube Experiment?
Explain his experiment in brevity using a diagram
12) What are cathode rays? Which subatomic particle does it now represent?
13) What is the Plum Pudding Model? Why is this model incorrect? Explain
his experiment in brevity using a diagram
14) What did Robert A. Millikan discover in his Oil Drop Experiment? Explain
his experiment in brevity using a diagram
15) What did Ernest Rutherford discover in his Gold Foil Bombardment
Experiment? Explain his experiment in brevity using a diagram
16) What are alpha particles? How do alpha particles play a major role in the
experiment?
17) Did Ernest Rutherford support or refute JJ Thomson’s Plum Pudding
Model? Why? Explain.
18) What did James Chadwick discover? Why is this important in terms of
John Dalton’s Atomic Theory?
19) What did Niels Bohr discover? Explain his model in brevity using a
diagram
20) Why is the Planetary Model of Niels Bohr not a correct model of the
atomic structure? Explain.
III. Periodic Table:
21) What did Stanislao Cannizzaro propose? Why? Explain.
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22) What did Dmitri Mendeleev propose? How did he organize the Periodic
Table?
23) What dilemma did he have with element Iodine and element Tellurium?
24) What did he do with empty spaces in his Periodic Table?
25) Are his predictions about the undiscovered elements true or not?
Explain.
26) What did Henry Moseley propose? H How did he organize the Periodic
Table?
27) Who is attributed with the Modern Periodic Table, Mendeleev or
Moseley? Why? Explain.
28) How did Moseley resolve the Mendeleev’s dilemma on Iodine and
Tellurium? Explain.
29) What did Glen Seaborg propose on the development of the Modern
Periodic Table?
30) Why is the arrangement of elements on the Modern Periodic Table so
important to chemists around the world?
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