Transcript Chemistry 111

Chemistry 111
Sections 5.1 – 5.8
Chemistry 111
1
Chapter 5
• Chapter 5 Topics
– Atom Concept (Dalton)
– Protons, neutrons &
electrons
– Nuclear Atom
(Rutherford)
– Isotopes, Nuclear
symbols
– Atomic Mass & Average
Atomic Mass
– Periodic Table
(Mendeleev)
– Elemental Symbols
• What we’ll do:
– Discuss Figures 5.3
& 5.4 (Rutherford)
– Quick Review of
Nuclear Symbols
– Average Atomic Mass
(Mathy)
– Review your chapter
notes, work on
Homework.
2
Rutherford Experiment
• Before:
– Thompson’s Plum
Pudding
Model of the Atom
• pudding = positively
charged matter
• plums = electrons
– Atoms are solid
chunks with (+) stuff
& electrons (-).
+
+ + +
+ + +
+
Pudding
+ Plums (e-)
= an Atom.
+
+ + +
+ + +
+
3
Rutherford Experiment II
• Experiment:
– Shoot alpha particles (2+ charge) at a thin
gold foil
– Should burn a hole & go straight through
• In the lab, they saw something else…
4
Rutherford Experiment Animation
5
Rutherford Experiment III
• Results /
Conclusions
– Now the atom is
mostly empty space
– Nucleus has positive
charge & most of
mass.
– Electrons in a
diffuse cloud
around the nucleus.
6
Nuclear Symbols
• The nuclear symbol is a format we use to
quickly specify a given isotope. You have to
memorize the exact format:
Z = atomic number = # of protons
A = mass number = #p + #n
Sy = elemental symbol
• Examples:
– Radioactive Carbon
14
6 protons, 14-6=8 neutrons
6
A
Z
Sy
235
92
U
C
– Bomb-quality Uranium
92 protons, 235-92=143 neutrons
7
Average Atomic Mass
• Isotopes:
 12C has Mass of A  12 amu or g/mol
 Period table gives 12.011 amu or g/mol
 Which is correct?
• Both:
 Natural Earth Carbon is a mixture of
14C.
 Table 5.2 shows:


12C
= 12.000000000 amu
13C = 13.003354826 amu
12C, 13C,
and
98.93 %
1.07 %
 Mass of periodic table is the weighted sum of
these numbers
8
Average Atomic Mass II
• Weighted Sum:
 Percent


Mass


 100
 12C
 98.93 %


12.000000


 100
 12C
.9893 12.000
12
C
11.87
 12.009  12.01

 Percent


Mass


 100
 13C
 1.07 %

 
13.003354826 
 100
 13C


0.0107 13.003 
13
C
0.139
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Team Exercise
• This chapter is mainly qualitative
– We will use the team activity to actively review the topics.
– Discuss what you don’t fully understand.
– Note topics that you want me to go over at the beginning of
Thursday’s class.
– Review your chapter notes.
– Discuss Textbook Problems (esp. # 25, 8)
– Consider an ad-hoc concept map?
• GOAL / ASSIGNMENT: Spend time actively
reviewing the material.
• Complete your active learning log.
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