radioisotopes - wordpress.com · radioisotopes figure 1: scientific and medical uses for some...
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Chemical bonds (Ionic)
Radioisotopes
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- can be stopped by a brick of lead
Radioisotopes✦ Radioisotopes - have an unstable nucleus and emit subatomic particles or energy as they decay into more stable atoms
alpha particles (α)
beta particles (β)
gamma rays (γ)
- a helium nucleus - can be stopped by a sheet of paper
What can stop them?
- high speed electrons- can be stopped by a sheet of lead- energetic electromagnetic radiation
α- paper sheet
β- lead sheet
γ- lead brick
✦ Radioactive emissions include:
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C14
6
20Ca
45
19K
40
53I
131
88Ra
226
Radioisotope Uses
Trace movement of carbon through biological pathways, like respiration and photosynthesis
Measures rate of bone formation
Half-life of 1.3 billion years (decays into 40Ar)Ratio of 40K : 40Ar used to date fossils
Taken up by thyroid glandGland can be imaged to detect abnormalities
Emits radiation that can destroy living cellsUsed to treat cancer tumors
Radioisotopes
Figure 1: Scientific and medical uses for some radioisotopes
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Radiation can damage cells
Extremely useful in diagnosis and treatment of diseases
Example 1: inject radioactive material into patient and trace its movement in the body
Example 2: energy emitted from radioactive decay can be directed to a tumour
Short half-life preferred
Radioisotopes in Medicine
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Tracer - radioisotope placed in body on biologically active molecule (glucose, water, or ammonia)
Give off gamma rays as they decay - easily detectable
How are TheyTraced?
PET scan of 47 y/o woman, shows leukemia present in bone marrow before treatment (left) and after chemotherapy (right)
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Ionic Bonds
Covalent Bonds
Polar Covalent Bonds
Chemical Bonds
✦ Chemical bonds are formed between atoms by interaction of their respective electrons
✦Three types of intramolecular bonds (bonds that hold atoms in a molecule together):
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Ionic Bonds
11p+
12no17p+
18no
Na+ Cl-
-
Electrostatic attraction
cation anion
✦ Ionic Bond - occurs when there is a transfer of one or more electrons from one atom to another
✦ Transfer leads to formation of a cation and anion ✦Resulting electrostatic attraction between these two oppositely charged ions is an ionic bond
+
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