The History of Atomic Structure. Democritus Named the atom from the Greek word “atomos” meaning...

Transcript of The History of Atomic Structure. Democritus Named the atom from the Greek word “atomos” meaning...

The History of Atomic The History of Atomic StructureStructure

Democritus

Named the atom from the Greek word “atomos” meaning indivisible.

Wrote that atoms were the smallest unit of matter to keep its identity.

http://www.svarog.org/filozofija/graph/democritus.jpg

http://www.uoregon.edu/~ch111/images/democritus.gif

John Dalton

England 1780’s All matter is made

up of atoms. All atoms of the

same element are the same.

Atoms combine in specific ratios.

There is nothing smaller than an atom.

http://images.google.com/imgres?imgurl=zebu.uoregon.edu/~js/21st_century_science/images/dalton_atoms.gif&imgrefurl=http://zebu.uoregon.edu/~js/ast123/lectures/lec04.html&h=201&w=383&prev=/images%3Fq%3Djohn%2Bdalton%26svnum%3D10%26hl%3Den

http://www.chemheritage.org/EducationalServices/webquest/dalton/dalton02.gif

J. J. Thomson Discovered the

electron while running electricity through a gas.

Discovered that electrons were negative.

“Plum pudding” model of the atom.

http://www.admin.cam.ac.uk/univ/innovation/thomson.jpeg

Marie & Pierre Curie

Provided evidence for the existence of protons and neutrons.

Discovered radium and polonium.

Marie Curie was the first female winner of the Nobel prize and the first double winner.

http://images.google.com/imgres?imgurl=www.chemmybear.com/radium.jpg&imgrefurl=http://www.chemmybear.com/radium.html&h=238&w=156&prev=/images%3Fq%3Dradium%26svnum%3D10%26hl%3Den%26sa%3DG

Ernest Rutherford

Discovered that the nucleus was positively charged and very tiny.

Found that the atom is mostly empty space.

http://library.thinkquest.org/3471/genesis2.jpg

Niels Bohr

Developed the “solar system” model of the atom.

The nucleus in the center of the atom is made of protons (+) and neutrons.

Electrons (-) orbit the nucleus like the planets around the sun.

http://images.google.com/imgres?imgurl=csep10.phys.utk.edu/astr162/lect/light/bohrframe/bohr2.gif&imgrefurl=http://csep10.phys.utk.edu/astr162/lect/light/bohr.html&h=204&w=205&prev=/images%3Fq%3Dbohr%26start%3D140%26svnum%3D10%26hl%3Den%26sa%3DN

Electron Cloud Model The current model

of the atom. Electrons do not

orbit the nucleus in orderly paths.

Electrons move around the nucleus at near the speed of light in a general area.

Research continues.

http://images.google.com/imgres?imgurl=www.mtsu.edu/~sschmidt/Cognitive/intro/cloud.jpg&imgrefurl=http://www.mtsu.edu/~sschmidt/Cognitive/intro/intro.html&h=283&w=281&prev=/images%3Fq%3Delectron%2Bcloud%2Bmodel%26svnum%3D10%26hl%3Den%26sa%3DG

Summary

Proton Don says “If all the elements are on the periodic table, where’s the cheese?”

http://www.funbrain.com/periodic/protondo.gif

Protons

Found in the nucleus of the atom.

Have a charge of +1

Have a mass of 1 atomic mass unit (amu)

Neutrons

Found in the nucleus of the atom.

Mass of 1 amu Neutrons have no

charge.

Electrons

Found in orbits (energy levels or shells) around the nucleus.

Travel at near the speed of light.

Charge is –1 Mass is 1/1800th

amu.

http://www.cnde.iastate.edu/ncce/K12/RT_K12/electrons/atom.jpg

What makes one element different from another?

The number of protons is always the same as the atomic number.

The number of electrons is usually the same as the atomic number.

To find the number of neutrons: take the atomic mass, rounded to the nearest whole number, and subtract the atomic number.

Finding the number of neutrons

The mass number of this isotope of lithium is 7.

Notice that 7 is equal to the total number of protons and neutrons.

If you remove the protons (atomic number), the neutrons are left.

Isotopes of HydrogenWhat do they have in common?

What are the differences?

The History of Atomic Structure. Democritus Named the atom from the Greek word “atomos” meaning...

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