The Atom Essay, Research Paper

The Atom

AP Physics Period 2

In the spring of 1897 J.J. Thomson demonstrated that the beam of glowing

affair in a cathode-ray tubing was non made of light moving ridges, as & # 8220 ; the about

consentaneous sentiment of German physicists & # 8221 ; held. Rather, cathode beams were

negatively charged atoms boiling off the negative cathode and attracted to

the positive anode. These atoms could be deflected by an electric field and

set into curved waies by a magnetic field. They were much lighter than

H atoms and were indistinguishable & # 8220 ; what of all time the gas through which the discharge

base on ballss & # 8221 ; if gas was introduced into the tubing. Since they were lighter than the

lightest known sort of affair and indistinguishable regardless of the sort of affair

they were born from, it followed that they must be some basic constitutional portion

of affair, and if they were a portion, so there must be a whole. The existent,

physical negatron implied a existent, physical atom: the particulate theory of

affair was hence justified for the first clip convincingly by physical

experiment. They sang success at the one-year Cavendish dinner.

Armed with the negatron, and cognizing from other experiment that what was

left when negatrons were stripped off from an atom was much more monolithic

balance that was positively charged, Thomson went on in the following decennary to

develop a theoretical account of the atom that came to be called the & # 8220 ; plum pudding & # 8221 ; theoretical account.

The Thomson atom, & # 8220 ; a figure of negatively electrified atoms enclosed in a

sphere of unvarying positive electrification & # 8221 ; like raisins in a pudding, was a

loanblend: particulate negatrons and diffuse balance. It served the utile

intent of showing mathematically that negatrons could be arranged in a

stable constellations within an atom and that the mathematically stable

agreements could account for the similarities and regularities among chemical

elements that the periodic tabular array of the elements shows. It was going

clear that the negatrons were responsible for chemical affinities between

elements, that chemical science was finally electrical.

Thomson merely missed detecting X beams in 1884. He was non so luckless

in fable as the Oxford physicist Frederick Smith, who found that photographic

home bases kept near a cathode-ray tubing were apt to be fogged and simply told his

helper to travel them to another topographic point. Thomson noticed that glass tubing held

& # 8220 ; at a distance of some pess from the discharge-tube & # 8221 ; fluoresced merely as the wall

of the tubing itself did when bombarded with cathode beams, but he was excessively captive

on analyzing the beams themselves to purse the cause. Rontgen isolated the consequence

by covering his cathode-ray tubing with black paper. When a nearby screen of

florescent stuff still glowed he realized that whatever was doing the

screen to glow was go throughing through the paper and step ining with the air. If

he held his manus between the covered tubing and the screen, his manus somewhat

reduced the freshness on the screen but in the dark shadow he could see his castanetss.

Rontgen & # 8217 ; s find intrigued other research workers beside J.J. Thomson and

Ernest Rutherford. The Frenchman Hernri Becquerel was a third-generation

physicist who, like his male parent and gramps before him, occupied the chair of

natural philosophies at the Musee Historie in Pairs ; like them besides he was an expert on

phosphorescence and fluorescence. In his instance, specific of U. He heard

a study of Rontgen & # 8217 ; s work at the hebdomadal meeting of the Academie diethylstilbestrols Sciences on

January 20, 1896. He learned that the X beams emerged from the fluorescence

glass, which instantly suggested to him that he should prove assorted

fluorescence stuffs to see if they besides emitted X beams. He worked for 10

yearss without success, read an article on X beams in January 30 that encouraged

him to maintain working and decided to seek a uranium spline, uranyl K sulphate.

His first experiment succeeded-he found that the uranium salt emitted

radiation but misled him. He had sealed a photographic home base in black paper,

sprinkled a bed of uranium salt onto the paper and & # 8220 ; exposed the whole thing to

the Sun for several hours. & # 8221 ; When he developed the photographic home base & # 8220 ; I saw the

silhouette of the phosphorescent substance in black on the negative. & # 8221 ; He

erroneously thought sunlight activated the consequence, much as a cathode beam releases

Rontgen & # 8217 ; s X rays from the glass.

The narrative of Becqueerel & # 8217 ; s subsequent serendipity is celebrated. When he

tried to reiterate his experiment on Feb. 26 and once more on February 27 Paris was

covered with clouds. He put the exposed photographic home base off in a dark

drawer, with the U salt in topographic point. On March 1 he decided to travel in front and

develop the drama, & # 8220 ; anticipating to happen the images really lame. On the reverse,

the silhouettes appeared with great strength. I thought a T one time that the

action might be able to travel on in the dark. & # 8221 ; Energetic, perforating radiation

from inert flatness

er unstimulated by beams or visible radiation: now Rutherford had his topic,

as Marie and Pierre Curie, looking for the pure component that radiated, had their

backbreaking work.

But no one understood what produced the lines. At best, mathematicians

and spectroscopists who liked to play with wavelength Numberss were able to happen

beautiful harmonic regularities among sets of spectral lines. Johann Balmer, a

nineteenth-century Swiss mathematical physicist, identified in 1885 one of the

most basic harmoniousnesss, a expression for ciphering the wavelengths of the spectral

lines of H. these jointly called the Balmer series.

It is non necessary to understand mathematics to appreciate the

simpleness of the expression Balmer derived that predicts a line & # 8217 ; s location on

spectral bad to an truth of within on portion in a 1000, a expression that has

merely on arbitrary figure: lambdda=3646 ( n^2/n^2-4 ) . Using this expression, Balmer

was able to foretell the wavelengths of lines to be expected for parts of the

H spectrum non yet studied./ They were found where he said they would be.

Bohr would hold known these expression and Numberss from undergraduate

natural philosophies particularly since Christensen was an supporter of Rydberg and had

exhaustively studied his work. But spectrometry was far from Bohr & # 8217 ; s field and he

presumptively had forgotten them. He sought out his old friend and schoolmate, Han dynasties

Hansen, a physicists and pupil of spectrometry merely returned from Gottigen.

Hansen reviewed the regularity of line spectra with him. Bohr looked up the

Numberss. & # 8220 ; As shortly as I saw Balmer & # 8217 ; s expression, & # 8221 ; he said subsequently, & # 8220 ; the whole

thing was instantly clear to me. & # 8221 ;

What was instantly clear was the relationship between his revolving

negatrons and the lines of spectral visible radiation. Bohr proposed that an negatron edge

to a nucleus usually occupies a stable, basic orbit called a land province. Add

energy to the atom, heat it for illustration, the negatron responds by leaping to a

higher orbit, one of the more energetic stationary provinces farther off from the

karyon. Add more energy and the negatron continues leaping to higher orbits.

Cease adding energy-leaving the atom alone-and the negatron leap back to their

land provinces. With each leap, each negatron emits a photon of characteristic

energy. The leap, and so the photon energies, are limited by Plank & # 8217 ; s invariable.

Subtract the value of a lower-energy stationary province W2 from the value of a

higher energy stationary province W1 and you can acquire precisely the energy of visible radiation as

hv. So here was the physical mechanisms of Plank & # 8217 ; s pit radiation.

From this elegant simplification, W1-W2=hv, Bohr was able to deduce the

Balmer series. The lines of the Balmer series turn out to be precisely the

energies of the photons that the H negatron emits when it jumps down from

orbit to revolve to its land province.

Then, sensationally, with the simple expression, R=2pi^2me^4/h^3, Bolar

produced Rydberg & # 8217 ; s constant, computation it within 7 per centum of its

by experimentation measured value. & # 8220 ; There is nil in the universe which impresses a

physicist more, & # 8221 ; an American physicist remarks, & # 8220 ; than a numerical understanding

between experiment and theory, and I do non believe that there can of all time hold been

a numerical understanding more impressive than this 1, as I can attest who

retrieve its advent. & # 8221 ;

& # 8220 ; On the fundamental law of atoms and molecules & # 8221 ; was seminally of import to

natural philosophies. Bexzides suggesting a utile theoretical account for the atom, it demonstrated that

events ensts that take topographic point on the atomic graduated table are quantized: that merely as

affair issues as atoms and atom s in a province of indispensable coarseness, so

besides does procedure. Procedure is discontinuous and the & # 8220 ; granule & # 8221 ; of mechanistic

natural philosophies was hence imprecise ; though a good estimate that worked for

large-scale events, it failed to account for atomic nuances.

Bohr was happy to coerce this confrontation between the old natural philosophies and

the new. He felt that it would be fruitful for natural philosophies. because original work

is inherently rebellious, his paper was non merely an scrutiny of the physical

universe but besides a political papers. It proposed, in a sense, to get down a reform

motion in natural philosophies: to restrict claims and clear up epistemic false beliefs.

Mechanistic natural philosophies had become autocratic. It had outreached itself to claim

cosmopolitan application, to claim that the existence and everything in it is

stiffly governed by mechanistic cause and consequence. That was Haeckelism carried

to a cold extreme. It stifled Neils Bohr as a biological Haeckelism and stifled

Christian Bohr and as a similar dictatorship in doctrine and in businessperson

Christianty had stifled Soren Kierkegaard.

Bibliography

Rodes, Richard. The Making of the Atomic Bomb. New York: Ssimon and Schuster,

1986.

& # 8220 ; Nuclear Wapon. & # 8221 ; The Enclopedia Britannica. Encylopedia Britannica In.

Chicago

V8 ; 1991, p 820-821.

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