Unit 2: history of atomic structure

23 terms by beckybryan 

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discovery of atomic structure

Dalton's conclusions for the existence of atoms are based on observations of how matter behaves
Atoms are too small to be seen
How did he, and other scientists of the time, "know" atoms exist?

Cathode Rays

In the mid 1800s it was discovered that radiation was produced when high voltage is applied to electrodes in a partially evacuated glass tube.

The rays themselves are invisible, however they cause certain materials, including glass, to fluoresce.

The rays were also observed to be deflected by the presence of a magnetic field.

J.J. Thompson

In 1897 published a paper that concluded, from his observations, that the radiation was a stream of negatively charged particles.
made paper that is generally accepted as the discovery of the electron.

Robert Millikan

went to University of Chicago, performed a series of experiments that determined the charge and mass of an electron.

charge

1.602e-19 Coulombs

Mass

9.10e-28 grams

radioactivity

spontaneous emission of radiation

Henri Becquerel

French scientist discovers in 1896 that a Uranium compound spontaneously emits high-energy radiation

earnest rutherford

discovers three types of radiation
Alpha (a)
Beta (b)
Gamma (g)

alpha

type of radiation
Fast moving particles called ... particles.
Charge; 2+
Mass; about 7400 times that of an electron

beta

type of radiation
Fast moving particles called ... particles that are really high speed electrons
Charge; 1-
Mass; about 7400 times that of an electron

gamma

type of radiation
High energy radiation similar to X-rays.
Does not consist of particles and does not have a charge

atoms are composed of smaller particles

The discovery of the electron and observation that some compound spontaneously emit radiation suggests that...

atoms are a uniform sphere of positive charge with negatively charged electrons embedded inside

J.J. Thompson proposed that...
He further said that because electrons are so small they contribute virtually nothing to the over mass of the atom itself.

J.J. thompson

made model of atom become know as the "plumpudding" model

raisins

negativly charged electrons in plum pudding model

pudding

possitivly charge spread throughout the sphere

The gold foil experiment

consisted of a beam of alpha particles shot at an extremely thin foil of gold

Rutherford

performed experiment known as gold foil experiment to tst thompson's plum pudding model

nucleus

in the gold foil experiment-Most of the mass of each gold atom and all of its positive charged are in a small, very dense, region called ...

protons/rutherford

In nucleus-Positively charged ...in 1919 by ...

neutrons/james chadwick

in nucleus-neutral... in 1932 by...

empty space

most of the total volume of the atom is...in which electrons move

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