Chapter 2, Part 2
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Transcript Chapter 2, Part 2
Announcements
•T E X T B O O K / C L I C K E R S
•H O M E W O R K - C H A P T E R 2 N O W P O S T E D , D U E 9 / 6
•L A B T H I S W E E K - P R I N T E X P E R I M E N T S , D O P R E -
LAB
•C H E M I S T R Y H E L P C E N T E R
Review- Atomic Symbols & Isotopes
• ATOM SYMBOLS
mass number→A
atomic number→Z
X
• ISOTOPES: Have same # protons, different # neutrons
• REVIEW EXAMPLE
32
15
P
How many protons does an atom of
phosphorus-32 have?
32
30
17
15
32
15
P
How many electrons does an atom of
phosphorus-32 have?
32
30
17
15
32
15
P
How many neutrons does an atom of
phosphorus-32 have?
32
30
17
15
32
15
P
It’s Time For Some Donut Math!
Dunkin Donuts sells both regular-sized donuts and
Munchkins
Let’s say that of all the donuts sold:
78.3% are regular-sized (mass= 57g)
21.7% are Munchkins (mass= 10g)
What is the weighted average mass of a Dunkin
Donut?
If Munchkins were more
abundant, would the average
mass of a Dunkin Donut go up
or down?
Isotopes and Average Atomic Mass
a
l
l
i
s
o
t
o
p
e
s
A
v
e
r
a
g
e
a
t
o
m
i
c
m
a
s
s
=
(
f
r
a
c
t
i
o
n
a
l
a
b
u
n
d
a
n
c
e
)
(
m
a
s
s
o
f
i
s
o
t
o
p
e
)
A Non-Edible Example
Silver has two isotopes:
Isotope
107
Ag
109
Ag
Mass (u)
% Abundance
106.905
51.839
108.905
48.161
What is the average atomic mass of Silver?
Mass Spectrometry Determines Mass:Charge
Mass spectrometry allows
us to determine the
natural abundances of the
different isotopes
What do these things have in common?
Floyd Landis Case
Landis won 2006 Tour de France
Tested positive for testosterone doping
Question #1: Did Landis have an abnormally high
testosterone level?
testosterone
epitestosterone
Isotopes and Steroid Testing
Question #2: Is the excess testosterone natural or
synthetic?
Isotope-ratio mass spectrometry (CIR) used to determine
the ratio of 13C to 12C in Landis’ testosterone
Photosynthesis prefers 12C
C3 plants: Strong preference for 12C
C4 plants: Less of a preference for 12C
Normal diet= mixture of C3 and C4 plants
Synthetic testosterone comes from soy, contains less 13C
13C:12C
reduced Landis “tested positive” for doping
The Periodic Table
Elements are arranged to highlight common
properties and trends
Arrangement reflects microscopic structure of atom
The Periodic Table- Groups and Periods
Main Group & Transition Elements
Metals, Nonmetals, Metalloids
Groups with Names
Periodic Table