group to project in science

8/2/2019 Group to Project in Science

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RADIATION

GROUP 2

IV- Amethyst

ALPHA, BETA AND GAMMA RAYS

NATURAL AND ARTIFICIAL

ISOTOPES

AND


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Types of Ionizing Radiation

The three major types of radiation are alpha, beta, and gamma.

ALPHA RADIATION

Alpha radiation occurs when a helium nucleus is emitted from aradioactive source.

Alpha particles are positively charged and are symbolized with the Greek

letter .

Alpha particles are not very penetrating. They can be stopped by a sheetof paper.


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BETA RADIATION

Beta radiation is created when a neutron breaks apart into aproton which remains in the nucleus, and a fast movingelectron which is released from the nucleus.

Beta particles are negativelycharged.

They are the size of an electron and can penetrate through about4 mm of body tissue, but they can be stopped bymetal foil.


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GAMMA RADIATION

Gamma rays are high energyphotons that are emitted from thenucleus of radioactive atoms.

Nuclei often emit gamma rays along with alpha or beta particlesduring radioactive decay. One example is the disintegration ofThorium-230 to Radium-226.

Gamma particles have no charge, are extremely penetrating,and can even go through several centimeters oflead and severalmeters of concrete.


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ERNEST RUTHERFORD studied the nature of the radiation.He discovered the alpha , beta and gamma rays.


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Alpha, beta particles andgamma rays


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TypeRepresentation Properties

Alpha (a)

Particleradiation

Consist of two protons and two neutrons, or, the nucleus of

a helium atom. They carry a positive charge of +2e. Theyare massive, but slow moving end their maximum speed isabout 0.1% the speed of light c. Alpha particles have verylittle penetrating power; they can penetrate no more than afew centimetres of air and absorbed by thick paper.However, alpha rays are able to ionize a large number ofatoms within the small area they were able to penetrate.

Beta (B)particleradiation

Beta radiation consists of electrons. A beta particle isemitted from the nucleus when a neutron becomes a protonand vice versa. The beta particle carries a charge of + / - e.Beta particles travel a little less than the speed of light or~0.9c. They can penetrate paper or several millimetres ofskin and about 1- metre of air. They are absorbed byaluminum or Perspex, a few millimetres thick. Their ionizingcapacity is less than that of alpha radiation.

Gamma (y)

rayphotons

A form of high-energy electromagnetic radiation that travelsat the speed of light, c. It has no electrical charge and hasgreat penetrating power. Not even a thick piece of lead orconcrete will stop all of them, although, their ionizingcapacity is smaller than that of beta rays.

-

+

Properties of nuclear radiation


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NATURAL AND ARTIFICIAL ISOTOPES


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Naming the Nuclides

The results of Rutherfords alpha scattering experiment were accounted for by

proposing that an atom consist of positive core called nucleus. The atom of an element iselectrically neutral the nucleus contains the protons and neutrons and a number ofelectrons equal to the number of protons reside outside the nucleus.

In 1902, Ernest Rutherford and Frederic Soddy first proposed that radioactivityproduces new elements. This idea led physicists and chemists to discover various elements.These new elements however, turned out to be chemically identical to other known

elements although they have different atomic masses.In 1913, Soddy proposed that an element could have different forms with

different atomic masses. He gave the name isotope to any one of the forms of the givenelement. It was later found that most elements have two or more isotopes, Some isotopeswere stable, while others are not. Even the simplest element, hydrogen. Has two stableisotopes namely. ordinary hydrogen and deuterium, and one unstable isotope, tritium.

When referring to the nucleus ofan atom, the term nuclide isused. Nuclides may representedby the symbol

A

Z X

mass

number

atomic

number

4

2He

Element

symbol


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Nuclear Stability

Atomic nuclei having even number of neutrons and protons are stable. Those with

even number of neutrons and protons are stable. Those with even numbers of neutrons and odd

number of protons, or odd number of both protons and neutrons, are usually unstable. Around 1800 different isotopes have been observed, but only 264 of these are stable. Of the 264 isotope,157 have an even number of protons and neutrons.

Atomic nuclei consist of protons and neutrons bound together by the residual strongforce. Because protons are positively charged, they repel each other. Neutrons,which are electrically neutral, stabilize the nucleus in two ways. Their copresence

pushes protons slightly apart, reducing the electrostatic repulsion between theprotons, and they exert the attractive nuclear force on each other and on protons.For this reason, one or more neutrons are necessary for two or more protons to bebound into a nucleus. As the number of protons increases, so does the ratio ofneutrons to protons necessary to ensure a stable nucleus (see graph at right). Forexample, although the neutron:proton ratio of 32He is 1:2, the neutron:proton ratio of23892U is greater than 3:2. A number of lighter elements have stable nuclides with

the ratio 1:1 (Z = N). The nuclide 4020Ca (calcium-40) is the heaviest stable nuclidewith the same number of neutrons and protons; all heavier stable nuclides containmore neutrons than protons.
http://en.wikipedia.org/wiki/Residual_strong_forcehttp://en.wikipedia.org/wiki/Residual_strong_forcehttp://en.wikipedia.org/wiki/Residual_strong_forcehttp://en.wikipedia.org/wiki/Residual_strong_force


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Periodic table colored according to the number of stable isotopes. Elements withodd atomic numbers have only one or two stable isotopes, while elements witheven atomic numbers all have three or more stable isotopes, except for the firstthree: helium, beryllium, and carbon.
http://en.wikipedia.org/wiki/File:Periodic_Table_by_Number_of_Stable_Isotopes.PNG


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http://en.wikipedia.org/wiki/File:Periodic_Table_Radioactivity.svg


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Periodic table with elements colored according to the half-life of their

most stable isotope. Stable elements; Radioactive elements withvery long-lived isotopes. Their half-live of over four million years confersthem very small, if not negligible radioactivities; Radioactiveelements that may present low health hazards. Their most stableisotopes have half-lives between 800 and 34.000 years. Because ofthis, they usually have some commercial applications; Radioactive

elements that are known to pose high safety risks. Their most stableisotopes have half-lifes between one day and 103 years. Theirradioactivities confers them little potential for commercialuses; Highly radioactive elements. Their most stable isotopes havehalf-lifes between one day and several minutes. They pose severe

health risks. Few of them receive uses outside basicresearch; Extremely radioactive elements. Very little is known aboutthese elements due to their extreme instability and radioactivitiy.


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And thats the report of group 2thank you!!!

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