Mrs. Howell’s Grade 9 Science: Acton District High School

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

The idea started around..The idea started around..

About 450 BCAbout 450 BC

The Greek The Greek philosopher philosopher

Empedocles Empedocles

stated that matter stated that matter consists of four consists of four

elements elements

-earth, air, fire & earth, air, fire & water-water- 450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700’s 1831AD 1879AD 1903AD1898AD1897AD 1911AD 1922AD

But about…But about…

About 400 BCAbout 400 BCThe Greek The Greek philosopher philosopher

Democritus Democritus

developed the first developed the first atomic hypothesis.atomic hypothesis.

- - All matter be subdivided All matter be subdivided only to a certain point, at only to a certain point, at which only atoms remainwhich only atoms remain. .

““Atomos”- Greek Atomos”- Greek word for indivisibleword for indivisible

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

Unfortunately...Unfortunately...

About 350 BCAbout 350 BCThe Greek philosopher The Greek philosopher

AristotleAristotleopposed Democritus' opposed Democritus'

idea of atoms and idea of atoms and dismissed it as worthless dismissed it as worthless

and promoted the 4 and promoted the 4 element model.element model.

Because of Aristotle’s Because of Aristotle’s great influence in the great influence in the

science world, this science world, this concept about matter concept about matter lasted for more than lasted for more than

2000 years.2000 years.450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700’s 1831AD 1879AD 1903AD1898AD1897AD 1911AD 1922AD

A.D. 500-1600A.D. 500-1600Arabian, Chinese and Arabian, Chinese and European European

AlchemistsAlchemists

studied matter, studied matter, experimenting with experimenting with different chemical different chemical substances.substances.

They devised the system They devised the system chemical symbols. chemical symbols.

-but they still used the -but they still used the four element systemfour element system--

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

A.D. 1650-1700’sA.D. 1650-1700’sRobert BoyleRobert BoyleAntoine LavoisierAntoine LavoisierJoseph PriestleyJoseph PriestleyHenry CavendishHenry CavendishFound that matter such Found that matter such as air and water were as air and water were made of a mixture of made of a mixture of pure substances.pure substances.

Their research promoted Their research promoted the idea of matter being the idea of matter being made of ‘elements’ and made of ‘elements’ and disproved the idea of the disproved the idea of the four element system .four element system .

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

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700’s 1855AD 1879AD 1898AD1897AD 1911AD 1922AD

1808 A.D. 1808 A.D. British scientist British scientist

John DaltonJohn Dalton

Pictured the atom as a Pictured the atom as a tiny, indivisible sphere tiny, indivisible sphere

much like a billiard ball.much like a billiard ball.

Further developed the Further developed the idea of ‘atom particles’ in idea of ‘atom particles’ in

his atomic theory .his atomic theory .

                            

 

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 of one 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.

1855 A.D. 1855 A.D. German scientist German scientist

Heinrich GeisslerHeinrich GeisslerA glassblower andA glassblower and

inventor of the sealed inventor of the sealed glass tubes that pumped glass tubes that pumped out air and discharged out air and discharged

electricity through gaseselectricity through gases..

-his invention helped -his invention helped lead to the next two atom lead to the next two atom

discoveries-discoveries-

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700’s 1855AD 1879AD 1903AD1898AD1897AD 1911AD 1922AD

450 BC 400 BC 350 BC 500-1600 AD 1808AD1650 AD Late 1700’s 1855AD 1879AD 1898AD1897AD 1911AD 1922AD

1879 A.D. 1879 A.D. British scientist British scientist

William CrookesWilliam Crookes

Discovered as the Discovered as the pressure was lowered in pressure was lowered in a electric gas discharge a electric gas discharge tube, the negative end tube, the negative end appeared to emit rays, appeared to emit rays,

now known to be a now known to be a stream of free electrons. stream of free electrons. This stream also could This stream also could push a tiny windmill in push a tiny windmill in

the tube.the tube.

Discovery of charged Discovery of charged particles and that they particles and that they

had mass .had mass .

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

1897 A.D. 1897 A.D. British scientist British scientist

J.J. ThomsonJ.J. ThomsonExperimented on the Experimented on the streams of particles streams of particles using magnets and using magnets and electric current and electric current and

discovered the pieces of discovered the pieces of atoms we know as atoms we know as

electrons and protons.electrons and protons.

- Proposed the “raisin - Proposed the “raisin bun” model of the atom. bun” model of the atom. Positive charged sphere Positive charged sphere with negatively charged with negatively charged particles embedded in it-particles embedded in it-

1897AD

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

Henri BecquerelHenri Becquerel

Pierre & Marie Pierre & Marie CurieCurie

Experimented with Experimented with natural radioactivity.natural radioactivity.

- Their work and the - Their work and the materials they discovered materials they discovered

greatly helped the next greatly helped the next proposed model of the proposed model of the

atom -atom -

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

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

1911 A.D. 1911 A.D. New Zealand New Zealand

scientist scientist

Ernest Ernest RutherfordRutherford

Experimented with Experimented with a radiation source a radiation source that sent out alpha that sent out alpha particles through a particles through a thin piece of gold thin piece of gold foil to a detector foil to a detector screen that glowed screen that glowed when it was hit.when it was hit.

Most particles Most particles passed through the passed through the foil, but 1 in 8000 foil, but 1 in 8000 bounced back!bounced back!

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

1911 A.D. 1911 A.D. Ernest RutherfordErnest Rutherford

Proposed that if the Proposed that if the particles bounced back particles bounced back that the atom must that the atom must consist of a tiny, dense, consist of a tiny, dense, positive core called a positive core called a nucleus and is nucleus and is surrounded by a cloud of surrounded by a cloud of moving negative moving negative electrons, and not a electrons, and not a sphere with embedded sphere with embedded electrons (JJ.Thomson’s electrons (JJ.Thomson’s idea).idea). -Discovered the second -Discovered the second sub-atomic particle of the sub-atomic particle of the atom: the proton (+) & atom: the proton (+) & new model for the atom -new model for the atom -

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

1922 A.D. 1922 A.D. Danish scientist Danish scientist

Niels BohrNiels BohrCame up with Came up with experimental evidence experimental evidence proving that electrons proving that electrons exist in energy levels exist in energy levels (shells) orbiting around (shells) orbiting around a positively charged a positively charged nucleusnucleus..

-Orbital electron energy -Orbital electron energy shells -shells -

1932AD

1932 A.D. 1932 A.D. English scientist English scientist

James ChadwickJames ChadwickUsing alpha particles Using alpha particles discovered a neutral discovered a neutral atomic particle with a atomic particle with a mass close to a proton. mass close to a proton. What he discovered was What he discovered was the neutronthe neutron..

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

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

                                           

History of the Atomic Theory

(see text pg 82 through pg 85 and 91) 

A. Fill in the Blank areas in this table during the lesson 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

Ancient Greece

Empedocles  

 

   

Ancient Greece

Democritus 

 

   

A.D. 500-1600

Alchemists Four element model

Elements like Zinc, Bithmuth, Phosphorous, and Arsenic

1650-late 1700’

Robert BoyleAntoine LavoisierJoseph PriestleyHenry 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

                               

     

Thank you!