Class 12 chemistry handouts prem dhawan sir (D.P.S r.k.puram's best chem teacher)Full description
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Chemistry Notes for Olevels Combined Chemistry
Radioactiv ity
Radioactivity - refers to the spontaneous emission of particles or highenergy electromagnetic radiation from the nuclei of unstable atoms. This occurs due to the disintegration of the atomic nuclei.
Discovery of Radioactivity In 1898 a French scientist, Antoine Henri Becquerel discovered the ability for uranium to create a picture hen e!posed to
Antoine Henri Bacquerel
Importance of Radioactivity Radioactivity has an importance mostly hen it comes to medicine, but is important for science in general. In medicine, radiation is used as a ay of $nding tumors ithin the body and then it is used to destroy them. %oever, in the realm of
Dangers of Radioactivity Radioactivity can damage cells' can cause burns, diarrhea, vomiting, infertility, migraine and death. ( huge amount of radioactivity can destroy many cells that the body cannot replace
Advantages and Disadvantages of Radioactivity Radioactivity does have a medical advantage. It is used for treatment of cancer patients to reduce or deplete tumors. (nother advantage is that it )ills microbes and permits carbon dating to ta)e place. ( disadvantage of radioactivity is that using it as a medical treatment does ) h d i
Types of Radioactivity The types of radioactivity are alpha, beta, and gamma, hich are classi$ed according to the charge if the electromagnetic rays they give o+. Alpha rays carry a positive charge, beta rays carry a negative one, and gamma rays are neutral.
amma ray
ISOTOPS •
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Isotopes are atoms of an element which have the same proton number but different nucleon number. Some isotopes are referred to as 'stable' and others as 'unstable' or 'radioactive'.
RADIOISOTOPS •
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Radioisotopes are unstable isotopes which decay and give out radioactive emissions. Radioisotopes are naturally occuring or artificially produced. Artificial radioisotopes can be produced when certain nuclides are bombarded by high energy particles.
PROPERTIES
OF
RADIOISOTOPES •
Emits radioactive radiation.
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Radioactive radiations can kill cells.
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Radioactive radiations have different penetrating ability with materials of different thickness and densities.
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Radioactive radiations can cause cell mutation.
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Radioactive radiations can ionize molecules.
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Its activity decreases with time.
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Radioisotopes have the same chemical properties as non-radioactive isotopes of the same element.
ARTI!I"IA# RADIOISOTOPS Example : hen a nucleus of magnesium!"# is bombarded by a neutron$sodium!"# can be produced.
Industry
("I(TI*/ *F R(0I*I/*T*/
$edicine To diagnose of thyroid disease using iodine-1!
To treat an overactive thyroid gland and certain kinds of thyroid cancer by using sodium iodide labelled with radioactive iodine
To detect position of blood clots or thrombosis using "odium-# in$ected in the bloodstream
To detect and treat brain tumor using phosphorus-!
To study the circulation of iron in the blood using iron-%&
To sterilize medical e'uipments and to destroy cancer cells in radiotherapy radioisotope cobalt-() is used
(2RI&"T&R To be used as tracers in the effectiveness of fertilizers using nitrogen1% and phosphorus -!
To induce genetic mutation in a plant in order to produce a better strain which has higher resistance against pest and diseases
Pests can be killed using radioactive rays esp. using gamma rays
To stop pests from reproducing, induced mutation by using gamma rays can be employed. But this has the probability of producing GMO and resistant pests
AR"HO#OG% -1# is another radioactive isotope that decays to -1. This isotope is found in all living organisms. 2nce an organism dies+ the -1# begins to decay. The half-life of -1#+ however+ is only %+3!) years. 4ecause of its short half-life+ the number of -1# isotopes in a sample is negligible after about %)+))) years+ making it impossible to use for dating older samples. -1# is used often in dating artifacts from humans.
*or determining age of fossils older than ()+))) years one uses a potassium-argon dating techni'ue. ,otassium dating has a half life of 1.! billion years+ thus allowing the age of rocks several billions years old to be determined. more accurate argonargon dating techni'ue /determining the ratio between argon-!& and argon-#)0 has also been developed.
To measure geological time.
5uring the formation of rocks+ some radioisotopes such as uranium-!6 are trapped. s the decay continues+ the proportion of uranium-!6 decreases slowly resulting in the e'ually slow growth of its product lead-)(. n estimate of the age of the rock can be inferred from the relative proportions of lead and uranium in the rock.
I&D'STRI S 1. The thickness of paper+ plastics+ clothes and metal sheets need to be standardized and this is done by placing a radioactive source at one side of the material and a detector on the other side. . *or sheets of metal+ gamma ray is used. *or plastics+ clothes and paper+ beta particles are used. !. The detector will register a higher count if the material is too thin and lower register if too thick. The computer will make ad$ustments according to the thickness of the material.
This mechanism is also used to ensure that containers such as cans and food packages are filled
!n order to kill germs that cause food to spoil "uickly, gamma rays are used.
to the specified amount.
!f e#posed to gamma ray, late# becomes Radioisotope is added to engine oil so that
