chapter 10 nuclear chemistry general, organic, & biological chemistry janice gorzynski smith
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CHAPTER 10Nuclear Chemistry
General, Organic, & Biological ChemistryJanice Gorzynski Smith
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CHAPTER 10: Nuclear Chemistry
Smith. General Organic & Biologicial Chemistry 2nd Ed.
Learning Objectives:
Interpret Atomic number and mass number Know radioactive particles: alpha, beta, positron,
gamma Write & solve radioactive decay equations Determine the number of half lives that pass in a
given amount of time. Familiar with measurements of the amount of
radioactivity Familiar with measurements of radiation absorbed Understand how radioisotopes are used in
medicine
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Nuclear Chemistry
Isotope Review
Smith. General Organic & Biological Chemistry 2nd Ed.
12
6C
mass number (A)
atomic number (Z)
the number of protons+
the number of neutrons
mass number (A)
number of protons
number of neutrons
6
12 – 6 = 6
atomic number (Z) = the number of protons
=
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Nuclear Chemistry
Radioactive Isotopes
Smith. General Organic & Biological Chemistry 2nd Ed.
•Of the known isotopes of all elements, 264 are stable and 300 are naturally occurring but unstable.
•A radioactive isotope, called a radioisotope, is unstable and spontaneously emits energy to form a more stable nucleus.
•Radioactivity is the nuclear radiation emitted by a radioactive isotope.
•An even larger number of radioactive isotopes, called artificial isotopes, have been produced in the laboratory.
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Nuclear Chemistry
Radiation
Smith. General Organic & Biological Chemistry 2nd Ed.
alpha particle: a or42
He
beta particle: β or 0−1
e
positron: β+ or 0+1
e
gamma ray: g A form of energy with no mass or charge
1
0n1
1p
neutronproton
+ 0
+1e
positron
Positrons are formed from protons
Beta particles are formed from neutrons1
0n
1
1p
neutron proton
+0
−1e
particle
Alpha particles are helium isotopes with 2 extra neutrons
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Nuclear Chemistry
Nuclear Reactions
Smith. General Organic & Biological Chemistry 2nd Ed.
A nuclear equation can be written as:
original nucleus
newnucleus
+ radiationemitted
The following must be equal on both sides of a nuclear equation :
•The sum of the mass numbers (A)
•The sum of the atomic numbers (Z)
Radioactive decay is the process by which an unstable radioactive nucleus emits radiation.
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Nuclear Chemistry
Nuclear Reactions
Smith. General Organic & Biological Chemistry 2nd Ed.
Alpha emission is the decay of a nucleus by emitting an a particle.
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Nuclear Chemistry
Nuclear Reactions
Smith. General Organic & Biological Chemistry 2nd Ed.
Beta emission is the decay of a nucleus by emittinga β particle; 1 neutron is lost and 1 proton is gained.
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Nuclear Chemistry
Nuclear Reactions
Smith. General Organic & Biological Chemistry 2nd Ed.
Positron emission is the decay of a nucleus by emitting a positron, β+; 1 proton is lost and 1 neutron is gained.
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Nuclear Chemistry
Nuclear Reactions
Smith. General Organic & Biological Chemistry 2nd Ed.
Gamma emission is the decay of a nucleus by emitting g radiation.
•The g rays are a form of energy only.
•Their emission causes no change in the atomic number or the mass number.
99m43 Tc +99
43 Tc g
Commonly, gemission
accompanies a or β emission.
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Nuclear Chemistry
Half-Life
Smith. General Organic & Biological Chemistry 2nd Ed.
The half-life (t1/2) of a radioactive isotope is the time ittakes for one-half of the sample to decay.
The half-life of a radioactive isotope is a property of agiven isotope and is independent of the amount ofsample, temperature, and pressure.
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Nuclear Chemistry
Half-Life
Smith. General Organic & Biological Chemistry 2nd Ed.
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Nuclear Chemistry
Detecting & Measuring Radioactivity
Smith. General Organic & Biological Chemistry 2nd Ed.
The amount of radioactivity in a sample is measured by the number of nuclei that decay per unit time: disintegrations per sec.
•Common units include:
1 Curie (Ci) = 3.7 x 1010 disintegrations/second
1 becquerel (Bq) = 1 disintegration/second
1 Ci = 3.7 x 1010 Bq.
Several units are used to measure the amount ofradiation absorbed by an organism.
•The rad—radiation absorbed dose—is the amount of radiation absorbed by one gram of a substance.
•The rem—radiation equivalent for man—is the amount of radiation that also factors in its energy and potential to damage tissue.
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Nuclear Chemistry
Detecting & Measuring Radioactivity
Smith. General Organic & Biological Chemistry 2nd Ed.
•The average radiation dose per year for a person is about 0.27 rem.
•Generally, no detectable biological effects are noticed for a radiation dose less than 25 rem.
•A single dose of 25–100 rem causes a temporary decrease in white blood cell count.
•A dose of more than 100 rem causes radiation sickness—nausea, vomiting, fatigue, etc.
•The LD50—the lethal dose that kills 50% of a population—is 500 rem in humans, while 600 rem is fatal for an entire population.
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Nuclear Chemistry
Radioisotopes Used in Medicine
Smith. General Organic & Biological Chemistry 2nd Ed.
•Radioisotopes can be injected or ingested to determine if an organ is functioning properly or to detect the presence of a tumor.
•Technetium-99m is used to evaluate the gall bladder and bile ducts and to detect internal bleeding.
•Thallium-201 is used in stress tests to diagnose coronary artery disease.
•Using a scan, normal organs are clearly visible, while malfunctioning or obstructed organs are not.
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Nuclear Chemistry
Radioisotopes Used in Medicine
Smith. General Organic & Biological Chemistry 2nd Ed.
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Nuclear Chemistry
Radioisotopes Used in Medicine
Smith. General Organic & Biological Chemistry 2nd Ed.
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Nuclear Chemistry
Radioisotopes Used in Medicine
Smith. General Organic & Biological Chemistry 2nd Ed.
•Positron emission tomography (PET) scans use radioisotopes which emit positrons which enable scanning of an organ.
•PET scans can detect tumors, coronary artery disease, Alzheimer’s disease, and track the progress of cancer.
•A PET scan is a noninvasive method of monitoring cancer treatment.