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8/20/2019 2A-1 Introduction to Atomic Structure v1
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What Is It Made Of ?
When it gives the required information
When and why do we want tocarry out elemental analysis ?
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Examples
Poisoning 1
Suspected arsenic, leador chromium poisoning
Analyze body fluids
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Poisoning
Determining the time of death
1
2
Analyze bone chemistry
Examples
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Poisoning
Determining the time of death
1
2
Elemental analysis of bullets 3
Forensic information about firearms use
Examples
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Cases
River Thames, London, September 2001
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Cases
How many peoplefired at JFK ?
John F Kenn
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Cases
Death of Napoleon
Napo
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What is an Element?
Robert Boyle (1627 – 1691)
Elements can neither be
created nor destroyed
Robert B
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What is an Element?
Elements are the basic building blocks
93 naturally occurring
Others created artificially
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What is an Element?
Common naturally occurring elements
H
O
C
Fe
Ag
Zn
Sn
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What is an Element?
Less common naturally occurring elements
U
Ir
Sm
Gd
Kr
Sb
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Paper
C, H, O
Burning a piece of paper
C CO 2
H H2O
Made of cellulose
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Human Body
CO 2
H2O
C, H, O, N, P, S, Ca, Na, K, Fe…
N oxides
P oxides
C
H
N
P
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Human Body
Au
Au or Hg in teeth
Hg oxides
Au
Hg
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The Periodic Table
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The Periodic Table
Dmitri Mendeleev
Dmitri Mende
Chemist
Organized the elementsaccording to chemistry
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The Periodic Table
Tom Lehrer
Tom Le
Mathematician and musician
Organized elements musically
http://www.youtube.com/watch?v=AcS3NOQnsQM
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Bulk composition
What is most of it made of ?
What Is It Made Of ?
Bul
Lead in bullets
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Trace impurities
What is a very smallpart of it made of ?
What Is It Made Of ?
Bul
Silver and antimony in bullets
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Analysis of elements
What Is It Made Of ?
Bulk composition 1
Trace impurities 2 More informative forforensic scientists
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Chemical Tests
Disadvantages
Large amounts of samples required
Destructive
Subject to interference
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Chemical Tests
Advantages
Fast
Easy to do
Simple equipment
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Trace Impurities
How small is small ?
S. I. prefixes for units
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S. I. Prefixes
1 Megagram 1 Mg 1 000 000 g 1 tonne1 Kilogram 1 kg 1 000 g1 milligram 1 mg 0.001 g 1 / 10001 microgram 1 µg 0.000 001 g 1 / 1000 000
1 nanogram 1 ng 0.000 000 001 g 1 / billionth1 picogram 1 pg 0.000 000 000 001 g 1/ trillionth
100 000 000 000 atoms 1 picogram
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Trace Impurities
Trace elements often measured in ppm
Part per million 1 per 1 000 000
1 g of 1 tonne 1 ppm
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Trace Impurities
5M people in Singapore
1 ppm = 5 people
Singapore m
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Trace Impurities
Trace elements often measured in ppm
Sometimes measured in ppb
Part per billion 1 per 1 000 000 000
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Trace Impurities
7B people in the world
7 000 000 000
World map
1 ppb = 7 people
