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Home , Atom, Atomic theory, James Chadwick, John Dalton, Niels Bohr

Welcome to 10/21/13 LT: I can Describe the evolution of the atomic • Weekend Stories • Warm Up • Portfolio • Notes and info card • Test make up TAT

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• What do you want to know about atoms? History of the Atom

Scientists and Their Contribution to the Model of an Atom History of the Atom - Timeline

Antoine Lavoisier J.J. Thomson makes a substantial discovers the number of contributions proposes and James to the of the Bohr proposes the Chadwick Model in Plum Pudding discovered 1766 – 1844 1913 the Model 1871in 1897 – 1937 1887 – 1961 in in 1932

460 – 370 BC

1700s 1800s 1900s 0

Erwin John DaltonErnest RutherfordSchrodinger proposes proposes performshis the Foildescribes the 1st atomic atomic theoryExperiment in in 1909the electron1891 – 1974 theory 1743 – 1794 1803 cloud in 1926

1885 – 1962

Click on picture for more information 1856 – 1940 Democritus (460 BC – 370 BC)

• Proposed an Atomic Theory that all atoms are small, hard, indivisible and indestructible made of a single material formed into different shapes and sizes. • did not support his atomic theory

Image taken from: https://reich- chemistry.wikispaces.com/T.+Glenn+ Time+Line+Project John (1766 – 1844)

 In 1803, proposed an Atomic Theory which states: o All substances are made of atoms; atoms are small particles that cannot be created, divided, or destroyed. o Atoms of the same element are exactly alike, and atoms of different elements are different o Atoms join with other atoms to make new substances  Calculated the atomic weights of many various elements

Image taken from: chemistry.about.com/.../John- Dalton.htm J.J. Thomson (1856 – 1940)

 Proved that an atom can be divided into smaller parts  While experimenting with cathode- ray tubes, discovered corpuscles, which were later called  Stated that the atom is neutral  In 1897, proposed the which states that atoms mostly consist of positively charged material with negatively charged Image taken from: www.wired.com/.../news/2008/04/d particles (electrons) located ayintech_0430 throughout the positive material  Won a (1871 – 1937)

 In 1909, performed the Gold Foil Experiment and suggested the following characteristics of the atom:

o It consists of a small core, or nucleus, that contains most of the of the atom

o This nucleus is made up of particles called , which have a positive charge

o The protons are surrounded by Image taken from: negatively charged electrons, but most http://www.scientific- of the atom is actually empty space web.com/en/Physics/Biographies/Er nestRutherford.html Niels Bohr (1885 – 1962)

 In 1913, proposed the , which suggests that electrons travel around the nucleus of an atom in or definite paths. Additionally, the electrons can jump from a path in one level to a path in another level (depending on their energy)

Image taken from:  Won a Nobel Prize commons.wikimedia.org/wiki/File:Ni els_Bohr.jpg  Worked with Ernest Rutherford

Erwin Schrodinger (1887-1961)

• In 1926, he further explained the of electrons in an atom by stating that the exact location of an electron cannot be stated; therefore, it is more accurate to view the electrons in regions called electron clouds; electron clouds are places where the electrons are likely to be found

Image taken from: • Did extensive work on the Wave nobelprize.org/.../1933/schrodinger  Schrodinger equation -bio.html • Won a Nobel Prize (1891 – 1974)

 Realized that the of most elements was double the number of protons  in 1932  Worked on the  Worked with Ernest Rutherford  Won a Nobel Prize

Image taken from: www.wired.com/.../news/2009/02/d ayintech_0227

Progression of the Atomic Model

------Electron Cloud - -- + +- + ------

The structure of an atom, according to: JamesErnestErwinJ.J.DemocritusNeils Schrodinger ThomsonChadwickRutherford Bohr & Atomic theory info card

• Complete info card for 1 of your choice for a timeline • Use page 582 for drawings