OChem/BioChem Chapter 12
Terms
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- Chemical Reactions
- involve the valence electron, of the atoms
- Nuclear Reactions
- do involve the nucleus and isotopes are very important.
- Discovery
- Triggered by the discovery of the x-rays even though x-rays are not nuclear phenomena
- Radiation
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pure form of energy and resulted from electrons moving from one energy level to another.
Ur gave off three types of radiation. When passed through a strong electric field or magnetic field, one portion when one way and another when the opposite way and the third didn't deflect at all.
Ernest Rutherford assigned the names of the three types of radiation - Alpha
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deflected the least
a stream of tiny particles identical to ( ) - Beta
- Deflected in the opposite direction and was a greater stream of electrons
- Gamma
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undeflected, had a different wavelength than visible and x-rays, pure radient form of energy
have no mass and no charge, having the most penetrating power. - Two other types
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positron - equal in mass but opposite in charge to the electron.
Electron Capture- process in which the nucleus absorbs an electron from an inner electron shell, usually first or second.
Accompanied by radiation and an x-ray is released. - Radiation Decay
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How radiation is produces. Nuclei that are unstable in nature undergo radiation decay.
ex. - Penetrating Power of Radiation
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determined by the mass of the particle. The more massive the particle the less its penetrating power
Alpha least penetrating. Alpha particles are helium nuclei which has a mass of 4
Beta: more penetrating that alpha. Electrons that make up the steam of beta particles = 0
Gamma: high- energy radiation with truly no mass and nochard, and the most penetrating power. - Curies (Ci)
- Rate at which nuclear disintergration takes occurs in a particular sample
- Ionizing radiation
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alpha, beta, gamma and x-rays are forms of ionizing radiation.
They cause the formation of the ions from nuetral particles.
in the body occurs most when water molecule and and ionizing energy interact with water molecules and forms reactive particles, which attack other molecules essential to proper cell function, thus damaging the living tissue. - REM
- meausre of the relative biological damage produced by a particular dose of radiation
- Half-life
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Radioactive isotope is characterized by a quantity called it's half-life.
The period in time in which one-half of the original number of atoms undergo radioactive decay. - Radioactive dating
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half life of certain isotopes can be used to estimate the ages of rock and archaeological artifacts.
Uranium-238 decays with a half life of 4.5 billion years.
Intial products of this decay are radioactive and brekadown continues until an isotope of lead is formed. (Lead-206) By measuring the relative amounts of uranium-238 and lead -206 scientist can estimate the age of a rock. - Artificial Transmutation and induce radioactivity
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Changing one element into another, by bombarding stabel nuclei with high-energy alpha particles, netrons or other subatomic particles.
nuclear medicine depends on the availability of a broad range of radioisotopes and many of these are artificially produced. - Nuclear Fission
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When a large UNSTABLE nucleus is bombarded by slow moving neutrons, the large nucleus breaks apart leaving two medium sized nuclei and releases more neutrons.
The energy released can be used to generate electric power like in a nuclear reactor.
or it can all be released at once as in a nuclear bomb
the products are radioactive, in a bomb these products are thrown in the atmosphere and reaches the ground as radioactive fallout, in a reactor these products must be periodically removed and stored. - Fusion
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Energy is released by the combination of two smaller nuclei into a large one.
accompanied by vast amount of energy.
Sun is powered by nuclear fusion of atomic nuclei. - Two important advantages of nuclear fusion over nuclear fission.
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1. Greater energy production per fusion even than fission event
2. Radioactive waster produced in a nuclear fusion is much more limited relative short half-life. - Nuclear Medicine
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Radio isotopes are used in nuclear medicine: therapeutically and diagnostic.
Radiation therapy is used to treat and cure disease such as cancer with radtion
radio isotopes provide information about the type or extent of illness.
Radioactive iodine-131 is used to determind the size, shape, and activity of the thyroid gland. And to treat thyroid cancer and control a hyper active thyroid
Gadolinium-153 is used to determine bone mineralization. - Medical Imaging
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Provides a mean of looking at internal organs without surgery.
The source of radiation is inside the body, soft tissues can be visualized by introducting materals that absorbs x=rays into the area to be studied.
Barium is used to view portions of digestive tract.
ex. computed tomography - Positron Emission Tomography (PET)
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used to measure dynamic processvoccurring in the body such as blood flow, the rate at which oxygen or gluclose is being metabolized.
PET can be used to pin-point areas of brain damage. - MRI and Ultra Sonography
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Both x-rays and nuclear radiation are ionizing radiations.
Both cause some tissue damage, but modern techniques keep the damage at a minimum.
Non-ionizing radiations:
Ultra Sonography: used in obstetrics to follow fetal development.
MRI: provides imagese of organs, and information about hte metabolic activity in particular tissues. Detects small tumors, blockages in blood vessels, damage to vertebral disc and problems in joints. - Other applications
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Elements that do not appear in nature can be prepared thru transmutation.
synthetic elements: 43,61,85 and the transuranium elemnts.
Chemical nad biochemical reaction mechanisms can often be determined only with radioactive traces.
Radio isoptopes are also used as sources for the irradiation of food stuff's as a method of preservation. The radiation destroys microorganisms that cause food spoilage.
Gamma irradiatin delays the decay of mushrooms.
Irradiated food shows little change in taste or appearence. There is no residual radioactiviy in the food after the sterilization process.