How can we help?

You can also find more resources in our Help Center.

23 terms

Unit 2: history of atomic structure

STUDY
PLAY
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