The Atom and Its History

7/25/2019 The Atom and Its History

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The Atom and its History


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Democritus (465

BC) Ancient Greeks came to

believe all matter consisted of differing

amounts of only 4 basic substances eart!" fire"#ater" and et!er

$euci%%us" teac!er of Democritus" %ro%osed

matter #as made of small %articles D& #as first to use t!e #ord atomos:

the smallest, indivisible part of matter


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Back in t!e 'ron Age&

ome elements are found in nature in a

relatively %ure form&

ulfur" co%%er" gold"

silver" and iron #ere

made into decorative

and useful ob*ects&


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+!e Alc!emists (Dark Ages till

t!e ,enaissance) $ooked for t!e

%!iloso%!ers stone

t!oug!t t!ey #ouldfind a #ay to turn -b

into Au

.e#ton dabbled in

alc!emy


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+!e modern age begins

/enning Brand of Germany discovered

%!os%!orusin 0661&

/e collected 52

buckets of urine"

fermented it" and

t!en boiled off t!e

#ater&


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3ose%! -riestley

Discovers oygen 04

(at t!e same time as

$avoisier 7 c!eel)

A 8natural %!iloso%!er9

Also credited #it!

inventing soda #ater:

(0;;0


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Antoine $avoisier $a# of conservation of

mass

Discovers nitrogen gas"and t!at oygen can be

c!emically se%arated

from certain com%ounds

confirms la# of definite

%ro%ortions

fat!er of modern

c!emistry loses !is !ead to t!e

=renc! ,evolution

04;014


8/53

3o!n Dalton

=at!er of modern

Atomic +!eory

t!oug!t atoms of anelement #ere all

identical and

indivisible

com%ounds are formed

from atoms of

different elements

0660


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Dalton>s model


10/53

William Prout

$a# of Definite

-ro%ortions

0


11/53

Dimitri ?endeleev (0


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?endeleev>s original table


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C!emistry and -!ysics 3oin

=orces+!e late 01t! century t!roug! t!e 2t!century


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3 3 +!omson Discovers t!e electron

-lum -udding ?odelof t!e atom&

All t!e c!arged

%articles #ererandomly scattered

like 8%lums in

%udding9

did not kno# aboutneutrons

.obel -rie 0126&

+!om%sons e%eriment to discoverelectrons (0


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+!omson>s model


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il!elm ,oentgen

0


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BecFuerel(0


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+!e Curies

-ierre ?arie

?arie (0


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.ikola +esla0


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Irnest ,ut!erford (0


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,ut!erford>s 8%lanetary9 model


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/enry ?osley (0


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J0

J +;

$os Alamos .ational $ab

,elations!i%s on t!e -eriodic
http://periodic.lanl.gov/default.htmhttp://periodic.lanl.gov/default.htm


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,elations!i%s on t!e -eriodic

+able


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Max Planck

t!e energy of an

orbiting electron isdetermined by t!e

freFuency of its #ave

0


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.eils Bo!r (0


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Bo!r>s energy level model


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Ir#in c!rLdinger

it! /eisenberg"

calculated %robable

locations of electrons

Kuantum mec!anics

and c!rLdinger >s cat

0


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$ouis de Broglie

Ilectrons orbiting t!e

nucleus e!ibit #ave

%ro%erties ?oving matter !as a

#avelengt! related to

its momentum

$eads to develo%ment

of t!e cloud model of

t!e atom

0


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Ilectron cloud model

Com%arisonof t!e t#o models
http://dwb4.unl.edu/ChemAnime/BOHRQD/BOHRQD.htmlhttp://dwb4.unl.edu/ChemAnime/BOHRQD/BOHRQD.html


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+!e 01 olvay Conference


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erner /eisenberg

?at!ematical models

#it! c!rodinger

+!e Mncertainty-rinci%le

you can not kno# bot!

t!e %osition and s%eed

of an electron

simultaneously

0120016


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/eisenberg #as a !ydrogen filled nai e%%elin t!at came to t!is

disastrous end in t!e 01;2>s&


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erner /eisenberg #as a German %!ysicist #!o" in !is late

t#enties" introduced #!at is kno#n as t!eHeisenberg

Uncertainty Principle. +!is discovery s!ook t!e very

foundation of subatomic %!ysics&


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/eisenberg>s %rinci%le states

=or any moment in time" it is

im%ossible to kno# t!e %osition and

t!e momentum of a moving %article&

im%ly because t!e act of observing affects t!e be!avior of t!e observed&


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'>m sure you>re a#are of some t!ings t!at c!ange t!eir be!avior

de%ending on !o# t!ey are being observed" for eam%le


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'n t!e case of %articles" t!e observer also affects t!e be!avior of

t!e observed& +!ere are limits to !o# muc! #e can kno# about a

%article at any given moment& +ake t!is %icture for eam%le

/o#ever" if #e moved t!e magnifying glass"

,ig!t no# #e can see t!e left side clearly&


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.o# #e can see t!e rig!t side clearly but can no longer see t!e left&


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'magine t!isA microsco%e t!at can see electrons in orbit around t!e nucleus

e s!oot ordinary lig!t #aves at t!e electron to find its

%osition"

e try gamma rays (s!orter #avelengt!)&

+!e %roblem #it! t!is is t!at gamma rays !ave so muc!

energy (!ig! freFuency)" t!at u%on contact" t!e electron

is knocked out of orbit making im%ossible to kno# itsmomentum&

but t!e #avelengt! is too long to be obstructed by

t!e electron"so&&&


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Albert Iinstein

0


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Iinstein didn>t like Kuantum

?ec!anics Iinstein to Bo!r" 8God

does not %lay dice

#it! t!e universe9 Bo!r" in res%onse"

8!o are you to be

telling God #!at to

doO9


45/53

-aul Dirac

=urt!er develo%ed Fuantum t!eory

from #ork of

/eisenberg and c!rodinger

!ared a .obel -rie 01;;

orked on Mranium

enric!ment during ''


46/53

3ames C!ad#ick

01; discovers t!e

neutron

I%lains isoto%es

!tt%PP###&nobel&seP%!ysicsPlaureatesP01;5Pc!ad#ickbio&!tml

0


47/53

$ise ?eitner

,ealied t!at some

#eig!t #as lost during

nuclear fission INmcB

as %art of t!e team

t!at discoverednuclear fission in late

01;2s

0


48/53

Inrico =ermi

(01200154)

Imigrated from =ascist 'taly in 01;< after#inning .obel -rie

Built first nuclear reactor underneat! t!e

stadium at t!e Mniversity of C!icago 014


49/53

Art!ur Com%ton

orked #it! =ermi on first reactor

Demonstrated t!e %article as%ect of

electromagnetic radiation

+!e Com%ton cattering Iffect

0


50/53

Glenn +& eaborg

0100111

,es%onsible for t!e

Actinide conce%t

Discovered ten elements

plutonium, americium,

curium, berkelium,

californium, einsteinium,

fermium, mendelevium,nobelium,and 106 named

after him!


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Radioactivity

+!ree ty%es

Al%!a Q a /e nucleus (%Jn)

Beta R an electron

Gamma S %ure energy I? #aves


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Penetration of Matter

+!oug! t!e most massive and most energetic ofradioactive emissions" t!e al%!a %article is t!es!ortest in range because of its strong interaction#it! matter& +!e electromagnetic gamma ray is

etremely %enetrating" even %enetratingconsiderable t!icknesses of concrete& +!e electronof beta radioactivity strongly interacts #it! matterand !as a s!ort range&


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The Atom and Its History