1.5.1 History of the Atomic Theory (Howell)

7/28/2019 1.5.1 History of the Atomic Theory (Howell)

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Mrs. Howells Grade 9 Science: Acton District High School


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450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1831AD 1879AD 1903AD1898AD1897AD 1911AD 1922AD Beyond
http://www.louisville.edu/provost/wroffice/bulb.gif


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The idea started around..

About 450 BC

The Greek philosopher

Empedocles

stated that matter

consists of fourelements

-earth, air, fire & water-

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1831AD 1879AD 1903AD1898AD1897AD 1911AD 1922AD


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But about

About 400 BCThe Greek philosopher

Democritus

developed the firstatomic hypothesis.

- Al l matter be subd iv ided

on ly to a certain poin t , at

which on ly atoms remain.

Atomos- Greek wordfor indivisible



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Unfortunately...

About 350 BCThe Greek philosopher

Aristotle

opposed Democritus' ideaof atoms and dismissed itas worthless and promoted

the 4 element model.Because of Aristotles great

influence in the scienceworld, this concept about

matter lasted for more than2000 years.



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A.D. 500-1600

Arabian, Chinese andEuropean

Alchemists

studied matter,experimenting withdifferent chemical

substances.They devised the systemchemical symbols.

-but they still used the fourelement system-

http://fyndo.myip.org/http://fyndo.myip.org/


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A.D. 1650-1700sRobert Boyle

Antoine LavoisierJoseph PriestleyHenry Cavendish

Found that matter such as

air and water were made ofa mixture of pure

substances.Their research promoted theidea of matter being made ofelements and disproved theidea of the four element

system .

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1831AD 1879AD 1898AD1897AD 1911AD 1922AD


8/19450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1855AD 1879AD 1898AD1897AD 1911AD 1922AD

1808 A.D.British scientist

John DaltonPictured the atom as a tiny,

indivisible sphere much

like a billiard ball.

Further developed the ideaof atom particles in his

atomic theory .


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Dalton's Atomic Theory - 1808

All elements are composed of atoms (indivisible

particles)

All atoms of the same element are identical - in

particular they have the same mass.

The atoms ofone kind of element are different from the

atoms of all other elements - in particular the atoms of

one element have a different mass than those of other

elements.

Atoms are indestructible and retain their identity in

chemical reactions.

Compounds are formed by joining atoms in specific

whole number ratios.


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1855 A.D.German scientist

Heinrich GeisslerA glassblower and

inventor of the sealed glass

tubes that pumped out airand discharged electricity

through gases.

-his invention helped leadto the next two atom

discoveries-





William CrookesDiscovered as the pressurewas lowered in a electric

gas discharge tube, thenegative end appeared to

emit rays, now known to bea stream of free electrons.

This stream also could push

a tiny windmill in the tube.Discovery of charged

particles and that they had

mass .


12/19450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1831AD 1879AD 1898AD 1911AD 1922AD


J.J. ThomsonExperimented on the

streams of particles usingmagnets and electric

current and discovered thepieces of atoms we know as

electrons and protons.

- Proposed the raisin bunmodel of the atom. Positive

charged sphere withnegatively charged particles

embedded in it-

1897AD


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1896-1898 A.D.French (Polish) scientists

Henri BecquerelPierre & Marie CurieExperimented with natural

radioactivity.

- Their work and thematerials they discovered

greatly helped the next

proposed model of theatom -

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1831AD 1879AD 1898AD 1911AD 1922AD1897AD


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1922 A.D.Danish scientist

Niels BohrCame up with experimentalevidence proving thatelectrons exist in energylevels (shells) orbitingaround a positively chargednucleus.

-Orbital electron energyshells -

1932AD


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1932 A.D.English scientist

James ChadwickUsing alpha particlesdiscovered a neutral atomicparticle with a mass close toa proton. What hediscovered was theneutron.

-Discovered the third sub-atomic particle of the atom:the neutron -

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700s 1831AD 1879AD 1898AD1897AD 1911AD 1922AD 1932AD


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History of the Atomic

Theory(see text pg 82 through pg 85 and 91)

A. Fill in the Blank areas in this table during thelesson or review the presentation on our class

website.

B. Draw the Atom Models of:Dalton J.J. Thomson Rutherford Bohr

Time

Perio

d

Scientists Atomic Model What discovery they

made

Ancien

t

Greec

e

Empedocles

Ancien

tGreec

e

Democritus

A.D.

500-

1600

Alchemists Four element

model

Elements like Zinc,

Bithmuth, Phosphorous,

and Arsenic

1650

-late

1700

Robert Boyle

Antoine Lavoisier

Joseph Priestley

Henry Cavendish

1808 John Dalton

1879 William

Crookes

1897 J.J. Thomson

(Nobel prize

1906)

1911 Ernest Rutherford(Nobel prize

1908)

1922 Niels Bohr

(Nobel prize

1922)

1932 James Chadwick(Nobel prize

1935)

Your task:

Work on filling out the

worksheet on the

history of the atom

table as well as

drawing the examples

of the models of the

atom on the bottom of

the sheet.

And


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Thank you!

1.5.1 History of the Atomic Theory (Howell)

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