Chapter 21 lecture notes modern chemistry

8/13/2019 Chapter 21 lecture notes modern chemistry

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Ch21_LectureNotes_2012.docpg 1of 13


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CH 21 LECTURE NOTES (2012)

BRIEF HISTORY

? Radiation accidentally discovered by Antoine Becquerel - 1896

- Uranium salt compounds; spots on photographic plates

? ierre and !arie "urie #associates o$ his% - sho&ed that rays $rom the U caused the

spots'

? RADIOACTIVITY term $rom !arie "urie

- (he process by &hich these rays are emitted

? RADIATION - the rays and particles that are emitted*comes from nucleus of atom - not proven till later

? RADIOISOTOPES - Unstable atoms that give o$$ radiation

- )ot all atoms or isotopes are radioactive

? Radiation is emitted in process called RA*+,A"(+. *."A/ #or nuclear decay%'

(his occurs &hen a nucleus becomes unstable0 usually due to the presence o$ toomany neutrons #overcro&ding2%0 or too $e& neutrons #not enough binding energy%'#Binding energy0 the usual stu$$ that holds the nucleus together0 can t 3%

? +n "hemical Reactions0 electrons are involved in the changes0 not the nucleus'

- "hemical reactions are a$$ected by temperature0 pressure0 catalysts'Nuclear cha!e" #$ $% &'$l'e elec%r$" and are not a$$ected by temperature0

pressure0 etc' Nuclear cha!e" ca$% e "e# u* "l$+e# #$+* $r %ure# $,, -

TYPES OF RADIATION (. /a$r)

Alha 4 heavy20 positively charged particle;structure identical to 5elium nucleus #no electrons%

)otation45e

7# t&o protons0 t&o neutrons eected $rom nucleus%

and

- slo&est moving0 lo& penetration po&er; easily shielded- does not typically penetrate beyond top sin layer

:)U".AR ),(A(+,)4"harge


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Be%a 4 light&eight particle2; negatively charged; is an electron)otation4

-1

e= # -1 charge0 = mass% and

#a neutron decays>changes into a proton and an electron' .lectron is eected%

- medium energy and penetration po&er; moderate shielding required

- can penetrate into deeper layers o$ sin

3a44a4 )ot a particle' is pure energy'

- )otation4 5

- no electrical charge0 no mass

- micro&aves etc' e?cept .R/ 5+@5 energy'

- is .lectromagnetic #&ave% radiation

: ?-rays are lo& energy gamma rays

6HAT HOLDS A NUCLEUS TO3ETHER7

? )uclei contain protons and neutrons' rotons are positively charged and should repel each

other strongly at that distance apart yet they stay together'

? )eutrons are no&n to play a role0 but ho& is still uncertain'

? (he glue that holds the nucleus together is called Binding Energy'

o "are$ul measurements o$ mass resulted in an amaCing $act3- the mass o$ a nucleus is .


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? (he Binding .nergy per )ucleon #ratio o$ energy to particle% is the most e$$ective measureo$ ho& stable a nucleus is'

(he chart on pg 67 sho&s that the middle elements0 masses o$ around 7=-6=0 have thehighest ratio0 and are there$ore more stable'

"Stability" is term used to describe how likely an atom (isotope) is to beradioactive. "Stable isotopes" are not radioactive. "Unstable isotopes" areradioactive.

? "ollected data on stability has resulted in a graph or chart &hich sho&s &hat is called the

Band o$


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IMPORTANT NOTES ABOUT USING THISCHART:

The X axis is the number o !rotons "or atomi# number$ an% is useu& as is'The ( axis is the number o neutrons) an% is oten NOT the most useu&' Inmost situations or usin*the#hart)+ou,i&&be*i-enanisoto!e.snotation)sho,natri*ht:The subs#ri!t is the atomi# number) the su!ers#ri!t is the MASS number'

To %etermine i the isoto!e is stab&e) +ou nee% to #au&ate the number oneutrons in or%er to &oo/it u! on the #hart' In this #ase) there are 012 3 24 5 164neutrons' 7 isoto!e is UNSTAB8E

? Rule" ,$r u"&! %he char% a$'e4

I"$%$e" %ha% are l$ca%e# & %he 9#$%%e# :$e9 are "%ale;

A< &"$%$e %ha% +$ul# e a$'e $r el$+ %he #$%%e# :$e are NOT "%ale a# +$ul#

e ra#&$ac%&'e;

"r

? .?amples47

H6

9878

"d

168HG+

D

D

D

Ch21_LectureNotes_2012.docpg Hof 13


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H6Ba

177D


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"arbon-17 decays into )itrogen-17 and emits an electron #beta particle%


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: !ass does ),( change0 but atomic number increases by 1' A ne& element results' (he

neutron decay itsel$ is represented by4

=n1

-- L1

51

J-1

e=

3a44a@ 3a44a ra#&a%&$ &" e%re4el< rare $ &%" $+ u% acc$4a&e" 4a< alha $re%a #eca


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Sa4le

)r$(le4"@

1% A substance has a hal$-li$e #5% o$ 1= days' +$ you start &ith a 7== gram sample0 ho& much

o$ the original is le$t a$ter G= daysI

7== ?== ? 1== ?H= ?H N'

7== ?== D 1= days0 == ?1== D 1= days0 1== ?H= D 1= days DD G= days'G 5al$-lives pass in G= days0 so cut in hal$0 G times'

A4$u% re4a&&! a,%er .0 #a


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URANIU/ 2.M DECAY SERIES

U062 a

Pa064 b

U064 a

Th069 a

Ra00 a

Rn000 a

Po012

a/b Pb014

b At012

a/b Bi014

a/b T&019

b Po014

aPb019

b Bi019

b Po019

a

Pb09 not radioactive

Thorium decay series ne!t pae#


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THORIU/ 2.2 DECAY SERIES

Th060

Ra002

A#002

Th002

Ra004

Rn009

Po01

Pb010

Bi010

T&092

Po010

Pb092

TRANSURANIU/ ELE/ENTS

- .lements &ith higher atomic numbers than Uranium

- none occur naturally0 and all are radioactive # decay or transmute2%

FISSION@

5 The s!&ittin* o a hea-+ atom or e&ement into sma&&er atoms "or e&ements$


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Usually caused by the collision o$ a neutron particle &ith a nucleus that is unstable

enough that such a collision &ill split it2'

* %eutron radiation is another type of radiation no discussed in your te!t.

(here are only (O, $issionable isotopes o$ elements used $or this purpose4 U-GH0 u-G9

* &-'() makes up only an e!tremely small percentae of &ranium isotopes.

* u-'(+ does not e!ist in nature, but can be created by some other nuclear reactions.

rimary products o$ UGH $ission4 Fr-91 0 Ba-17 and G neutrons'

(he three neutrons emitted are able to $ission other nearby Uranium atoms'

Oith su$$icient concentration o$ those atoms0 a Chain Reaction &ill occur0 resulting a

nuclear e?plosion #Atomic bomb%'


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6EB LINS@

"ontrolled vs Uncontrolled issions4

http4>>&&&'visionlearning'com>library>$lashSvie&er'phpIoidDG6=

@eneral +n$o0 A)* lash simulation o$ po&er plant4

http4>>&&&'h-phy'org>energy>po&er>print>nuclearSphySprintSe'html

5iroshima Bomb Run and citiCen unpreparedness4 : /ou(ube:

http4>>&&&'youtube'com>&atchIinde?DTvD)7aOER*gTlistD*M1A=6".1M8=A*H

Atomic bombs have tremendous destructive po&er both $rom its blast2 and the radiation released

to the AR@. surrounding area' "iviliCed nations are unliely to use an atomic &eapon againas a $irst strie because o$ the number that other nations have' !utually Assured *estruction2

)o &inner in such an attac'
http://www.visionlearning.com/library/flash_viewer.php?oid=3602http://www.hk-phy.org/energy/power/print/nuclear_phy_print_e.htmlhttp://www.hk-phy.org/energy/power/print/nuclear_phy_print_e.htmlhttp://www.youtube.com/watch?index=2&v=NF4LQaWJRDg&list=PLD7F1A06CE1780AD5http://www.visionlearning.com/library/flash_viewer.php?oid=3602


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CONTROLLED FISSION REACTIONS NUCLEAR PO6ER

+$ the concentration o$ U $uel atoms #density o$ them in a mi?ture% is lo& enough0 and the rate o$collisions $rom neutrons can be controlled0 a $ission reaction chain can be controlled'

(his is done in nuclear reactors4

U.S. NUCLEAR PLANT DESIN

Y$u ee# %$ $+ %he a4e,uc%&$ $, /AOR ar%" $, reac%$r "


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(he surrounding to&n &as evacuated but in looing bac0 that &as considered to be

slo&er than should have been'

- the to&n is still vacant' (he reactor is encased in a thic0 concrete T steelsarcophagus2' (his structure is sho&ing signs o$ cracing0 and people are tryingto determine &hat to do ne?t &ith it'

Three 4&le I"la# (U;S;)@ arch 19!9- most serious U'human error' A de$ective sensor indicated coolant levels inthe reactor &ere too high' ,perators $ailed to double chec &ith other sensors andreleased &ater causing the reactor to overheat'

- the problem &as detected early enough that the reactor &as shut do&n be$ore any

e?plosion occurred' (here &as a minor lea2 o$ radioactive material into the

atmosphere0 but no long term e$$ects have resulted'

- o$ all reactors currently operating0 construction on all o$ them began B.,R.

19M7'


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5 Bomb test aci$ic ,cean4

http4>>&&&'youtube'com>&atchIvD5VHbGH5v8W.

IONIIN3 RADIATION@

- nuclear radiation that can ioniCe2 other atoms by nocing a&ay their electrons

@[email protected] ",U)(.R4 detects radiation by detecting ions in a gas0 created &hen the

radiation causes them to lose electrons

+! BA*@.4 photographic $ilm is sensitive to nuclear0 ioniCing radiation and gets darer&ith e?posure' By checing ho& blac2 the $ilm is0 sa$ety people can monitor to maesure people are less liely to be e?posed to e?cessive radiation'

*,


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Cher$

Chapter 21 lecture notes modern chemistry

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