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Democritus
His theory: Matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. This piece would be indivisible. He named the smallest piece of matter “atomos,” meaning “not to be cut.” -
Isaac Newton
-suggested that atoms are held together with attractions(forces)
-stated "matter is formed of solid, massy impenetrable particles”
-theorized a mechanical universe with small, solid masses in motion -
Dmitri Mendaleev
created the Periodic Table -
J.J Thomson
~He changeed the whole view of the atom by discovery what we call electrons.
~Thomson’s atomic theory suggested that the atom is not indivisible as it was of smaller pieces – electrons and protons
~Proved that
-An atom consists of a sphere of positive charge with negatively charged electron embedded in it
-The positive and the negative charges in an atom are equal in magnitude -
Marie Curie
-created the Theory of Radioactivity
-discovered radium and polonium -
Hans Geiger
-invented a device that detected alpha particles -
R.A Millikan
-determined the unit charge of the electron
-allowed scientists to understand and find weight of subatomic particles -
Ernest Rutherford
His atomic theory states that the atom as having a central positive nucleus surrounded by negative orbiting electrons.
-This model suggested that most of the mass of the atom was contained in the small nucleus, and that the rest of the atom was mostly empty space. -
H.G Moseley
-discovered that the number of protons in an element determines its atomic number. -
James Chadwick
discovered the existance of a neuron
discovered they had no charge -
Niels Bohr
-his atomic structure theory stated the outer orbit of an atom could hold more electrons than the inner orbit -
HEISENBERG
-created foundation of the Quantum Theory
-best known for the development of the matrix mechanics formulation of quantum mechanics
Principle of Indeterminancy - you can not know both the position and velocity of a particle. -
John Dalton
-created a theory that included democritus's.
Believed that:
-All matter is made of atoms. Atoms are indivisible and indestructible.
-All atoms of a given element are identical in mass and properties.
-Compounds are formed by a combination of two or more different kinds of atoms.
-A chemical reaction is a rearrangement of atoms.
-Atoms can be neither created nor destroyed.
-also discovered color blindness -
Lise Meitner
-along with other scientist, discovered nuclear fission
