Radioative Kini

7/31/2019 Radioative Kini

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RADIOACTIVE


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RADIOACTIVE

http://www.youtube.com/watch?v=

v3mxM3JKDC4
http://www.youtube.com/watch?v=v3mxM3JKDC4http://www.youtube.com/watch?v=v3mxM3JKDC4http://www.youtube.com/watch?v=v3mxM3JKDC4http://www.youtube.com/watch?v=v3mxM3JKDC4


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Daltons Model English Chemist John Dalton

(1766-1844) referred to as thefather of atomic theory.

John Dalton (1808) proposedthe Atomic Theory. According toDalton, matter is made up of tinyparticles called atoms.

The atom is the smallest particleof matter that takes part in achemical reaction.

Atoms are indivisible and cannotbe created or destroyed. Further,atoms of the same element are

identical in every respect.http://suite101.com

http://www.syvum.com/cgi/online/serve.cgi/squizzes/chem/atomic1.html
http://suite101.com/http://www.syvum.com/cgi/online/serve.cgi/squizzes/chem/atomic1.htmlhttp://www.syvum.com/cgi/online/serve.cgi/squizzes/chem/atomic1.htmlhttp://suite101.com/


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Thomsons Model

J. J. Thomson (1897)discovered electronsin Cathode Ray

experiments. According to Thomson,

atoms are divisible.Atoms contain very tiny

negatively chargedparticles calledelectrons.


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Rutherford Model

In 1909, New Zealandphysicist Ernest Rutherford,along with Hans Geiger andErnest Marsden at theUniversity of Manchester,

performed a famousexperiment in order to putthe plum pudding model ofthe atom to the test.

Let us see:Rutherford Gold

Foil Experimenthttp://www.youtube.com/watch?v=Q8RuO2ekNGw
http://www.youtube.com/watch?v=Q8RuO2ekNGwhttp://www.youtube.com/watch?v=Q8RuO2ekNGwhttp://www.youtube.com/watch?v=Q8RuO2ekNGwhttp://www.youtube.com/watch?v=Q8RuO2ekNGw


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Chadwicks Model

James Chadwick(1932) disoveredneutrons. According to

Chadwick, atomscontain neutral particlescalled neutrons in their

nucleus along with thesubatomic particles (i.e.,electrons and protons).


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Bohrs Model

N. Bohr (1940) providedthe modern concept ofthe atomic model.

According to Bohr, the

atom is made of a centralnucleus containingprotons (positively-charged) and neutrons(with no charge).

The electrons (negatively-charged) revolve aroundthe nucleus in differentimaginary paths calledorbits or shells.


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TODAYS MODEL


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An atom of an element is represented

by its symbol as above.

A is for nucleon number Z is for protonnumber and X is forelement

The totalnumber of

protonsand

neutrons in

a nucleus

The number ofprotons in a

nucleus


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http://../Physics/P&P%20Recources/SPLASH/Flash/Radioaktif/helium.swfhttp://../Physics/P&P%20Recources/SPLASH/Flash/Radioaktif/helium.swf


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The proton number of aluminium is13,

The nucleon number of aluminium is27The number of neutron in this nucleus

is 14 (27 -13)


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IsotopesWhat it meant by the isotopes ?

isotopes are atoms of the same element with thesamenumber of protonsbutdifferent number of neutron.

In other words.

Atom is missing a neutron or has an

extra neutron


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carbon -12

carbon -14


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Radioisotopes

Radioisotopes are isotopes that areunstable and release radiation.

All isotopes are not radioisotopes.

In an unstable atom, the nucleus changesby giving off a neutron to get back to abalanced state.

As the unstable nucleus changes, it givesoff radiation and is said to be radioactive.Radioactive isotopes are often calledradioisotopes.


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1. What is meant by the radioactivity ?Radioactivityis thespontaneousandrandomemission or disintegration of an

unstable nucleus accompanied by theemission of energetic particlesor

photonsto become more stable.

RADIOCTIVITY

Radioactivity is the release of energy

and matter due to a change in thenucleus of an atom.


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2.The process is said to be spontaneousbecause

-It isnot influencedby any physicalfactors such as temperature, pressure,time , etc

3. The emission of radioactive rays israndom means that :

a) emission occurs atirregular intervals

b) emission doesnot occur at the samerate
http://../all%20about%20physics/SPLASH/Flash/Radioaktif/beta.swf


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RADIOACTIVITY

an alpha particle (we use the symbol)a beta particle (symbol )a gamma ray (symbol )


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Radioactive Detectors

1. Photographic Films

2. Gold Leaf Electroscopes3. Cloud Chambers

4. Geiger Muller Tube ( G.M Tube )


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PHOTOGRAPHIC FILMS


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SPARK COUNTER


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GOLD LEAF ELECTROSCOPES


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GOLD LEAF ELECTROSCOPE

suitable for detecting alpha particles becausealpha particles have high ionizing power.


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CLOUD CHAMBER

alpha

particlesare bestfor this

CLOUD CHAMBER


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CLOUD CHAMBERWhen the radioactive rays enter he upper part ,

the ionisation of air will occur. The ions allow thesaturated alcohol vapour to condense forming tiny

alcohol droplets and will cause the formation of

misty tracks.

The cloud chamber can detect all the three typesof radioactive radiation.


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GEIGER MULLER TUBE

Actual reading = Reading recorded

Background Reading.


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No Radiactive

emissionDectector Reason

1. Beta and

gamma.

Photographic

Films

Cannot penetrate through the metal

2. Alpha Gold LeafElectroscopes

Strong ionising power

3. Alpha, beta

and gamma

Cloud

Chambers

Tracks of alpha thicks and straight.

Beta

thin and twistGammathinner than beta.

4. Alpha, betaand gamma

Geiger

Muller Tube (

G.M Tube )

Alpha is positive charge , unlike

charge are attracted in a strong

electric field between the two

electrodes.5. Alpha, beta

and gamma

Geiger

Muller Tube (

G.M Tube )

The exposure of radiation over one

week -AGM tube connected to the

scaler.

Minimum intensity of a radiation.-

AGM tube connected to a ratemeter


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Characteristics RadioactiveEmissions


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http://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-

magnetic-field.html
http://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.htmlhttp://www.passmyexams.co.uk/GCSE/physics/properties-of-radiation-electric-magnetic-field.html


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Alpha particles are easy to stop, gamma rays are hard to stop.


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The reason alpha decay occurs is because thenucleus has too many protons which causeexcessive repulsion. In an attempt to reducethe repulsion, a Helium nucleus is emitted.

ALPHA DECAY


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1. Alpha


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238U "parent" nuclide, for example,produces234Th as the "daughter" nuclide.


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BETA DECAY

Beta decay occurs when the neutron to proton ratiois too great in the nucleus and causes instability. Inbasic beta decay, a neutron is turned into a protonand an electron. The electron is then emitted.


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2. Beta


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90Sr "parent" nuclide, for example,produces90Y as the "daughter" nuclide.


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GAMMA DECAY

Gamma decay occurs because the nucleus is attoo high an energy. The nucleus falls down to alower energy state and, in the process, emits a highenergy photon known as a gamma particle


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3. Gamma


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RADIOACTIVE DECAY SERIES


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RADIOACTIVE DECAY SERIES

For heavy nuclei

it often occursthat the daughternuclei, whichhave beenformed byradioactive

decay, decayagain to formnew daughternuclei and so on,until finally, aftermany decay

processes, astable nucleus isleft.


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Decay curve


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The half - life of radioactive source is the

time taken for halfof the radioactivenuclei to decay.

Half Life


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The count rate halves every 15 hours. So we say

its half life is 15 hours.


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Pa takes 20.8 hours to shrinks

from 80 g to 5 g.

a) How many halflives are there

80g 40g 20g 10g 5g

T T T T

( This decay process has taken the

time of 4 half lives )20.8 hours = 4 T , T = 20.8 / 4

= 5.2 hours.


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Calcium-45 Studying plant nutrition.

Carbon-14 Treating brain tumors, measuring age of ancientobjects.

Cobalt-60 Treating cancer, irradiating food, inducingmutations.

Iodine-131 Studying and treating the thyroid gland, finding

leaks in water pipes.

Iron-59 Studying the blood.

Sodium-24 Diagnosing circulatory disease.

Strontium-90 Treating small lesions.

Sulfur-35 Studying the body's use of certain amino acids.

Phosphorus-32 Studying plants' use of fertilizer.


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Smoke Detectors

Thickness Control

Sterilising

Radioactive Dating

Radioactive Tracers

Cancer Treatment


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NUCLEAR ENERGY

Nuclear energy is

the energy released during thesplittingand fusingof atomic nuclei


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ATOMIC MASS UNIT

One a.m.u. is

one twelfthof mass of a C -12 atom.

1 a.m.u. = 1.66 x 10-27 kg


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In most nuclear reaction the sum ofmasses of the particles before the reactionis more than the sum of the masses after

the reaction. The difference is called mass defect.

E = mc2

E energy releasedm mass defect

c- the speed of light; 3.00 x 108 ms-1

ATOMIC MASS UNIT


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NUCLEAR FISSION

Nuclear fission is

a process in which a heavy nucleus splits

into two or more lighter nuclei. Usually nucleus of an atom bombarded

with a neutron.


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NUCLEAR FISSION

When a uranium-235 is bombarded by aneutron , it is split into two fission fragments(Kripton-131 and Barium-142 ) and three freeneutrons.


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NUCLEAR FISSION

Radioactive element Atomic mass unit, u

U- 235 235.0492Rb93 93.92157

Cs141 140.91963

Neutron 1.00867

1. In a nuclear reaction U- 235 is bombarded by aneutron giving Cs 141, Rb 93 and 2 neutronsand energy is released .From table below , determine the energy released

when one U 235 atom undergoes such a nuclearreaction.


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1a.m.u = 1.66 x 10 -27kgc = 3.00 x 108 m s -1

U + n Rb + Cs + 2 n + energy

Total mass of product m1= 93.92137 + 140.91963 + 1.00867 x2= 236.85854 a.m.u

Total mass of reactant , m2= 235.10492 + 1.00867=236.05787 a.m.u

Mass defect = m1- m2= 236.85854 236.05787=0.80067 a.m.u= 0.80067 x 1.66x 10-27kg

= 1.3291122 x 10-27kgE = m c2= 0.80067 x 1.66 x 10-27x(3.00 x 108)2

=1.3291122 x 10-27kg x(3.00 x 108)2=11.96 x 10-11J


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CHAIN REACTION

In fission reaction one neutron bombardto one nucleus.

Another 2 or 3 neutron produced and canbombard another nucleus.

More fission will occur, in this way chain

reaction produced.
http://../all%20about%20physics/SPLASH/Flash/Radioaktif/chain2.swf


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NUCLEAR FUSION

In fusion reaction

two light nuclei combineto form a

heavier nucleus, releasing a vast amountof energy during the process.


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NUCLEAR FUSION

energynHeHH 1

0

4

2

3

1

2

12.01410 u 3.01605 u 4.00260 u 1.00867 u

What is the energy produced ?

2.820672 x 10-12J


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Negative Effects of Radioactive Substances

1. Radioactivewastes are considered dangerouswaste

2. The negative effects of radioactive waste dependon..

a) quantity of waste

b) the type of waste

c) the half- life of wasted) the type of radioactive rays emitted

3 Long half lives threaten our health

4. Radioactive waste must be kept in a special thick

barrel made of lead or concrete5. The barrel containing the radioactive waste then

buried in unused mines or non residential areas.

Safety Precautions


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Safety Precautions

1.Leadis used to block radioactive rays2. Use distance controller or tongsto move

radioactive materials3. The uniformworn by workers in a nuclear plant

must be kept in special bags4. Worker in radioactive energy station must wear

badgesto which the worker have beenexposed to radioactive rays can bedetermined.

5. Nuclear reactorshould be build on islands orareas far away from residents

6. Barrels containing radioactive materials mustbe labeled Radioactive materials and mustcarry the radioactive symbol.


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Properties

Radioactive

Half - life Rays /Radiation

Nucleon

numberRadioacti

vity

U 432 years Alpha 95 20

V 1620 years Alpha, betagamma

226 10

W 6 hours Gamma 99 50

X 5.27 years Gamma 60 25Y 15 days Beta 32 30


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235

92

1

0

92

36

141

56

1

0

U.+

n

Kr..+

Bax

n235 1.01 91.91 140.91 ?

a.m.u a.m.u a.m.u a.m.u


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Radioative Kini

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