Radioactivity And Radioactive Decay Pdf
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Radioactivity refers to the particles which are emitted from nuclei as a result of nuclear instability.
What Is Radioactivity?
Radioactivity , property exhibited by certain types of matter of emitting energy and subatomic particles spontaneously. It is, in essence, an attribute of individual atomic nuclei. An unstable nucleus will decompose spontaneously, or decay, into a more stable configuration but will do so only in a few specific ways by emitting certain particles or certain forms of electromagnetic energy. Radioactive decay is a property of several naturally occurring elements as well as of artificially produced isotopes of the elements.
What Is Radioactivity? How Does Radiation Affect Humans? What causes radioactivity? As its name implies, radioactivity is the act of emitting radiation spontaneously. This is done by an atomic nucleus that, for some reason, is unstable; it "wants" to give up some energy in order to shift to a more stable configuration. During the first half of the twentieth century, much of modern physics was devoted to exploring why this happens, with the result that nuclear decay was fairly well understood by Too many neutrons in a nucleus lead it to emit a negative beta particle, which changes one of the neutrons into a proton.
Too many protons in a nucleus lead it to emit a positron positively charged electron , changing a proton into a neutron. Too much energy leads a nucleus to emit a gamma ray, which discards great energy without changing any of the particles in the nucleus. Too much mass leads a nucleus to emit an alpha particle, discarding four heavy particles two protons and two neutrons.
How is radioactivity measured? Radioactivity is a physical, not a biological, phenomenon. Simply stated, the radioactivity of a sample can be measured by counting how many atoms are spontaneously decaying each second. This can be done with instruments designed to detect the particular type of radiation emitted with each "decay" or disintegration.
The actual number of disintegrations per second may be quite large. Scientists have agreed upon common units to use as a form of shorthand.
Thus, a curie abbreviated "Ci" and named after Pierre and Marie Curie, the discoverers of radium  is simply a shorthand way of writing "37,,, disintegrations per second," the rate of disintegration occurring in 1 gram of radium.
The more modern International System of Measurements SI unit for the same type of measurement is the becquerel abbreviated "Bq" and named after Henri Becquerel, the discoverer of radioactivity , which is simply a shorthand for "1 disintegration per second.
Being unstable does not lead an atomic nucleus to emit radiation immediately. Instead, the probability of an atom disintegrating is constant, as if unstable nuclei continuously participate in a sort of lottery, with random drawings to decide which atom will next emit radiation and disintegrate to a more stable state.
The time it takes for half of the atoms in a given mass to "win the lottery"--that is, emit radiation and change to a more stable state--is called the half-life. Half-lives vary greatly among types of atoms, from less than a second to billions of years.
For example, it will take about 4. Iodine , commonly used in medicine, has a half-life of only eight days. What is a radioactive decay chain? Stability may be achieved in a single decay, or a nucleus may decay through a series of states before it reaches a truly stable configuration, a bit like a Slinky toy stepping down a set of stairs.
Each state or step will have its own unique characteristics of half-life and type of radiation to be emitted as the move is made to the next state. Much scientific effort has been devoted to unraveling these decay chains, not only to achieve a basic understanding of nature, but also to design nuclear weapons and nuclear reactors.
The unusually complicated decay of uranium , for example--the primary source of natural radioactivity on earth--proceeds as follows:  U emits an alpha Thorium emits a beta Protactinium emits a beta Uranium emits an alpha Thorium emits an alpha Radium emits an alpha Radon emits an alpha Polonium emits an alpha Lead emits a beta Bismuth emits a beta Polonium emits an alpha Lead emits a beta Bismuth emits a beta Polonium emits an alpha Lead , which is stable How can radioactivity be caused artificially?
Radioactivity can occur both naturally and through human intervention. An example of artificially induced radioactivity is neutron activation. A neutron fired into a nucleus can cause nuclear fission the splitting of atoms. This is the basic concept behind the atomic bomb. Neutron activation is also the underlying principle of boron-neutron capture therapy for certain brain cancers.
A solution containing boron is injected into a patient and is absorbed more by the cancer than by other cells. Neutrons fired at the area of the brain cancer are readily absorbed captured by the boron nuclei.
These nuclei then become unstable and emit radiation that attacks the cancer cells. Simple in its basic physics, the treatment has been complex and controversial in practice and after half a century is still regarded as highly experimental.
Radioactivity , property exhibited by certain types of matter of emitting energy and subatomic particles spontaneously. It is, in essence, an attribute of individual atomic nuclei. An unstable nucleus will decompose spontaneously, or decay, into a more stable configuration but will do so only in a few specific ways by emitting certain particles or certain forms of electromagnetic energy. Radioactive decay is a property of several naturally occurring elements as well as of artificially produced isotopes of the elements. The rate at which a radioactive element decays is expressed in terms of its half-life ; i.
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Hamilton, Joseph H. Last reviewed: September A phenomenon resulting from an instability of the atomic nucleus in certain atoms whereby the nucleus experiences a spontaneous but measurably delayed nuclear transition or transformation with the resulting emission of radiation. The most commonly found types of radioactivity are alpha Fig. Each is characterized by the particular type of nuclear radiation which is emitted by the transforming parent nucleus. In addition, there are several other decay modes that are observed more rarely in specific regions of the periodic table Table 1.
Radioactive decay occurs when an unstable atomic nucleus loses energy by emitting energy in the form of emitted particles or electromagnetic waves, called radiation. Isotopes are atoms of the same element thereby having the same number of protons which differ in the number of neutrons in their nucleus. Some isotopes of a given element are more unstable than others, causing a nuclear reaction which releases energy to achieve a more stable nuclear configuration. There are many types of emmitted particles and radiation that radioisotopes produce when they decay.
Many nuclei are radioactive; that is, they decompose by emitting particles and in doing so, become a different nucleus.
CH103: Allied Health Chemistry
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he received the noble prize in physics. Radioactivity can be categorized chiefly according to their nuclear energetics into; alpha-decay.
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