Atomic Theories


John Dalton

Approx. 1803

Elements are made of invisible particle called atoms.
"Atoms are not created or destroyed by chemical processes".
All atoms are the same on an element.
When atoms are from a different element they have a different atomic weight.
In chemical reactions the atoms os an element are combined forming a compound.
Experiment example: He measured reactions and look at other scientists measurments.

Joseph John Thomson

Approx. 1890

Thomson's contribution to the concept of atomic structure.
"It's easy to extract negatevily charged particles from atoms"
The experiments he made were based on the "Cathode Rays" which consisted in looking at the conduction of electricity through a gas at low pressure applying high voltage through a discharge tube. The reults consisted in the preassure of the gas. The process gave as a result the gass tube to fluoresce (aka Cathode Rays).

Ernest Rutherford

Approx. 1909

There was polemic about how was the charge of an atom distributed, so base on the Thomson´s theory he made an experiment:
WIth a gold leaf in plum puddin only some aplha particles will deviat and some others will pass.
In a nuclear atom the particles shoud pass staright through it, every time they pass a zinc light will shine.
1 out of 1800 lighted, the hypthesis was correct. Most of the atom is just empty space, the center (nucleous) is positive and it is orbited by small negative particles (electrons).
He published it´s results on 1911.

Niels Bohr

Approx. 1911

Bohr's theory of electron orbits
Electrons orbiting around the nucleus should be continually emiting radiation
Radius cintinually shrinking
This was his first assumption which is wrong but later on he would find a better statement and continuing his research he wold find the other theory.

Niels Bohr

Approx. 1913

He started his investigation with the simpliest atom (Hydrogen).
"The force holding the electron in orbit, is the electrostatic force of attraction, between the positively charged proton and the negatively charged electron".
And so now he made a hypothesis which is better know now as "atomic scale" - Bohr's Quantum Hypothesis.
Electron Shell- each shell is know as n. The larger the number, the further the nucleus is the electron.

Werner Heisenberg


Heisenberg was the one who explianed how is the pattern movement of the electrons that surrounds the atom, this is called "The Quantum Mechanics"
He worked together with Bohr.

Erwin Schrödinger

Approx. 1926 - Approx. 2001

Schrödinger worked together with Heinsenberg.
He he gave a "derivation" of the wave equation for time-independent systems.
He discovered how the electrons worked and moved around the waves.