A Brief History of the Atom!

By: Stephanie Thaler

Picture from: http://www.ndt-ed.org/EducationResources/HighSchool/Electricity/atommodels.htm

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Listen closely my students and you will hear all the

fuss…that was created by the

Greek philosopher Democritus.

A long time ago in the city of Greece,

Democritus was pondering chalk and it’s smallest piece.

“I wonder” he said looking down at the floor,

“If after a certain point the dust can’t be broken down

anymore.” “a very small piece indeed,”

thought Democritus, “I shall call this small piece

atomos.”

Picture from: http://darkside.hubpages.com/hub/democritus

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Many years later an additional man,whose name was John Dalton came

up with a plan. He agreed that

atoms where the smallest you could

go, but thought things

needed to be tested before they could be confirmed

as so.

He developed some rules that explicitly

stated atoms could not be

destroyed or created. Another idea he had that was fantasticalWere that atoms of the same element must be identical.

Picture from: http://www.chemistryland.com/CHM130S/05-EarlyAtom/EarlyAtom.html

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Because Dalton’s theories could now be

testedhis atomic model ended

up being bested. “The atom” said

Thomson, “must have two sections,

which means that your model needs some minor

corrections.”“Compared to these

pieces the atom is large,It is made up of negative electrons embedded in a

positive charge.”

Picture From: http://mdkchemistry.blogspot.com/2013/01/111-rutherfords-experiment-and-atomic.html

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Soon Thomson’s ideas were left out in the cold

by Rutherford and his foil of gold.

“Your model,” said Rutherford, “doesn’t make sense.”

“The whole inner filling is much to dense.”

“My experiments are showing me this is the gist,

a small dense inner sphere called the nucleus is where the positive charges exist.

And instead of electrons being stuck there like glue,

there is mostly empty space between the two.”

“I agree to a point,” Stated Bohr with a sigh,

“But your placement of electrons seems wrong, I’ll tell

you why.”“If we look at your model, the

one right below, We can see that the electrons have somewhere they want to

go. The positive charge is pulling

them in,The solution must be there is

some sort of spin. But moving so much would cause the electrons to tire,

A situation that I fear might be dire.”

Picture from: http://www.rsc.org/chemsoc/timeline/pages/1911.html

Photo from: http://c85c7a.medialib.glogster.com/media/61/614ff53e2c77dd2dba10b4903e339b9008cccfd87beb0af2d252639e0cda4cdb/rutherford-20model.gif

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“Suppose for a second, pretend if you would,

The electrons don’t lose any energy, now that would be

good. What if like a planet they travel

a circular path,Without losing energy, though

that seems to defy math.”The world was aghast, that

couldn’t be right!Scientists tried to disprove him

with all their might!

Once it was agreed that Bohr’s model passed the test,

Chadwick stated “I might have the rest.”

“Now you state right here the number of protons and

electrons must be the same, Yet in your model the mass

can’t be explained!The explanation you give

seems a bit dubious, my conclusion must be there is something else in the nucleus.

Photo from: http://www.epa.gov/radiation/understand/rutherford.html

Photo from: http://www.universetoday.com/46886/bohrs-atomic-model/

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Now the model we’ve seen is mostly alright,

But the idea that an electron path can be

predicted isn’t quite right. The best we can do is

make a prediction,Claiming with certainty

would be fiction. Electron orbital uses

abound,They tell us where

electrons are probably found.

As the number of electrons in an atom rises,

The orbitals vary in shapes and sizes.

We’ll be discussing the orbitals in additional

chapters, I know the idea puts you in

raptures. For now just remember the

parts of the whole,We’ll also be discussing

atoms more when we talk about a mole.

Protons and neutrons exist in the center,

Electrons rotate in a probable manner.

Most of the atom is made up of empty space,

Except for a dense spot called the nucleus in the

center of the place. Photo from: http://faculty.clintoncc.suny.edu/faculty/michael.gregory/files/bio%20101/bio%20101%20lectures/chemistry/chemistr.htm

The End!