http://www.almaden.ibm.com/vis/stm/images/ibm.tif
http://www.almaden.ibm.com/vis/stm/images/cover7.tif
209
83
Bi
N/Z = 1.52
N/Z too high:
β− decay: ie emit e− from the nucleus and turn a neutron into a proton n emission: ie lose a neutron
Mass too high:
α decay: lose a 4He nucleus
β− decay: lose an e‐ from the nucleus turning a neutron into a proton
γ emission (high energy radiation) often accompanies nuclear decay processes
N/Z too low:
β+ decay: lose an e+ from the nucleus turning a proton into a neutron
e- capture: turn a proton into a neutron
Stable Nuclides
131I is used for internal treatment of thyroid cancer (only the thyroid uses iodine). It is also a major contaminant from the damaged Japanese nuclear reactors
131
0
0
131
Xe
+
e
+
I t1/2 = 8 days
54
‐1
0γ
53
t1/2 = “half‐life”, the time taken for half the initial sample to decay
e.g. γ‐camera image of 131I (from NaI solution) uptake in a normal and diseased thyroid gland, showing localisation of iodine.
18F is incorporated into molecules like glucose and is used in positron emission tomography (PET scanning) for metabolic function and cancer detection:
18
9 F
18
0 +
O
+
+1 e
8
t1/2 = 109.7 min
Seeing
Hearing
Speaking
Thinking
Reading
99mTc is the most commonly used radioactive isotope (>85%) used for
medicine scans together with a gamma camera:
99
42
Mo
99m
43Tc
99m
0 ‐
Tc
+
e
43
‐1
99
0
Tc
+
4 3
0γ
t1/2 = 6 hours
Technetium pyrophosphate is used to target bones and identify bone cancer, as in this gamma camera image.
nuclear 14C is used in radiocarbon dating:
14
0
B
+
7
‐1 e
t1/2 = 5568 years
The ambient 14C level increased due to atmospheric nuclear testing, peaking in 1962 ‐ known as the “Bomb Pulse.”
This has been accurately tracked over time as the deviation from the pre‐bomb isotope ratio, δ14C, and can be used to accurately determine the (recent) age of carbon‐containing materials.
E.g. wine dating & detecting false labels or blends.
dating drug crops.
Zoppi, et al., Nuclear Instruments and Methods in Physics Research B 223–224 (2004) 770–775
http://ndep.nv.gov/lts/upshot.jpg
14
6 C Ionic Crystals: NaCl
en.wikipedia.org/wiki/Sodium_chloride
Na+
Cl-
stress
Covalent Bonding
electron
nucleus
repulsion
http://courses.cm.utexas.edu/biverson/ch310n
oxygen
silicon
Covalent Networks
Diamond
Silica
Carbon Dioxide (Dry Ice)
δ−
δ+
δ−
http://www.llnl.gov/str/Yoo.html
Sugar (Sucrose)
http://csi.chemie.tu-darmstadt.de/ak/immel/graphics/gallery/sucroses.html
Water
High mp/bp
High liquid density
(ice is less dense)
High surface tension...
δ+
δ−
δ+
δ−
δ+
δ+
δ−
Metals
Copper
from the LIFE Science Library book Matter
Silver
Gold
http://www.museum.mtu.edu/Gallery/Jpegs/cop1642.jpg
www.topfoto.co.uk/gallery/tutankhamun
Metallic Bonding
Delocalised electrons
Metallic Bonding
Small
stress
Layers begin
rolling over
each other
Layers fall back
to original place
Stress
released
Large
stress
Layers deform
Alloys
Large
stress
Large
stress
Dislocations