-
Period: 460 BCE to 370 BCE
Democritus
-origin idea of atoms existing (athomos=indivisible)
-variety in shape and size -
Period: 384 BCE to 322 BCE
Aristotle
-did not believe in the origin idea (atomic theory)
-his theory: matter is made of the four elements (wind,earth,water,fire) -
Period: to
Dalton
-substances break down into elements
-elements consist of atoms (combination of identical/different atoms)
-atoms can be identical in size, shape,…(same element)
-atoms can not be created/destroyed -
Period: to
Thomson
-discovery of electrons (“corpuscles”) in 1897
- plum pudding/cookie model: electrons in the atom with no order -
Period: to
Rutherford
-gold foil experiment
—> discovery of the nucleus and protons -
Period: to
Bohr
-influenced by Max Planck and Albert Einstein
-planetary model/center stage:
-electrons can jump from one level to another
-they can not exist in between the levels -
Period: to
Schrödinger
-theory about the behavior of electrons (waves)
-possibility of calculating the exact energy levels of these waves -
Period: to
Chadwick
-discovery of particles without any electric charge (neutron)
-combination of neutrons an protons
—> nucleus -
Period: to
Heisenberg
-Quantum model/cloud model:
-4 orbitals (negatively charged—> holding 2 electrons)
-nucleus (positively charged)
-atom is neutralized
-uncertainty principle:
-it is impossible to determine the exact speed and position of
electrons