byErdal ERSOY

Your taskMake a PowerPoint presentation on how our

ideas about atomic structure have changed over the last 2500 years.

This template will help you.

There is information on page 372 in Physics for You.Your teacher may give you an Extension Sheet with some facts. You can find more from the Internet. See the next slide to find out how.

DemocritusDemocritus thought

matter could not be divided infinitely.

But he had no proof.He did this by

dividing a cheese into pieces until it couldn’t be divided by a knife.

John DaltonDalton’s elements that we

still think of as elements today;

Hydrogen,Carbon,Nytrogen

Oxygen,Phosphorus,Shulphur

Iron,Zinc,Copper,Lead, Gold,

Platine, Mercury

DALTON’S MODEL OF ATOM

All matter is made of atoms.

Atoms of an element are identical

Each element has different atoms.

Atoms are rearranged in reactions.

J. J. Thompson In this model, the atom is

composed of electrons surrounded by a soup of positive charge to balance the electron's negative charge, like negatively-charged "plums" surrounded by positively-charged "pudding".

Thompson’s experiment was important, and kick-started an entire wave of discovery of sub-atomic particles, including the next step in understanding the atom – the discovery of the atomic nucleus.

Brownian Motion TheoryThe importance of the theory lay

in the fact that it confirmed the kinetic theory's account of the second law of thermodynamics as being an essentially statistical law.

We know that a water molecule is about 0.1 by 0.2 nm in size, whereas a pollen particle is roughly 25 µm in diameter, some 250,000 times larger. So the pollen particle may be likened to the balloon, and the water molecules to the fans except that in this case the balloon is surrounded by fans.

Ernest Rutherford

JJ Thompson’s ‘plum-pudding’ says that negative electrons are in a positive framework.

The Rutherford’s method says that atoms are mostly empty space and negative electrons orbit a positive nucleus.

Find an image of Ernest Rutherford and place it here.

Alpha-particle scatteringGEIGER and MARSDENRutherford had a large

water tank installed on the ground floor of the building in Manchester, to carry out research on defense against submarine attack. Nevertheless, occasional research on alpha scattering continued. Scattering from heavy nuclei was fully accounted for by the electrostatic repulsion, so Rutherford concentrated on light nuclei, including hydrogen and nitrogen.

James ChadwickAs they studied atomic

disintegration, they kept seeing that the atomic number  was less than the atomic mass. For example, a helium atom has an atomic mass of 4, but an atomic number of 2. Since electrons have almost no mass, it seemed that something besides the protons in the nucleus were adding to the mass. He called them neutrons.

Isotopes is the atoms which has same atomic number but different neutron number.

Quarks

MURRAY GELL-MAN’S IDEASMurray Gell-Mann found that all of those particles,

including the neutron and proton, are composed of fundamental building blocks that he named "quarks." The quarks are permanently confined by forces coming from the exchange of "gluons." He and others later constructed the quantum field theory of quarks and gluons, called "quantum chromodynamics," which seems to account for all the nuclear particles and their strong interactions." ...

QUARKS Quarks combine to form 

composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. Due to a phenomenon known as color confinement, quarks are never found in isolation; they can only be found within hadrons.

Try to find an image for here, that will help to explain.

Extra TaskDemocritus (440 BC) suggested the idea of atoms but with

no proof. Eventually Robert Boyle’s experiments (1662) supported the idea and in 1738 Daniel Bernoulli proposed the kinetic theory.

John Dalton used atomic weights (1805) to support the idea, and in 1831 Thomas Graham investigated diffusion.

Henri Becquerel discovered radioactivity (1896) and Marie Curie discovered radium (1898). Ernest Rutherford discovered alpha and beta rays. Rutherford came up with the idea of an atomic nucleus.

Niels Bohr (1913) suggested the idea of electrons in orbits with different energies.

Write a slide or more about the new ideas that each of these scientists brought to the topic.

References http://web.mit.edu/philos/www/mm/democritus.jpg http://en.wikipedia.org/wiki/Plum_pudding_model http://upload.wikimedia.org/wikipedia/commons/thumb/f/ff/Plum_pudding_

atom.svg/348px-Plum_pudding_atom.svg.png http://www.coolfusion.com.au/img/LASERScan_2.png http://en.wikipedia.org/wiki/Brownian_motion http://www.scientific-web.com/en/Physics/Biographies/images/

ErnestRutherford2.jpg http://web.educastur.princast.es/proyectos/grupotecne/archivos/

investiga/145chadwick.jpg http://en.wikipedia.org/wiki/Quark http://en.wikipedia.org/wiki/File:Quark_structure_proton.svg http://www.osti.gov/accomplishments/gellmann.html