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322
Aristotle
His idea conflicted with Democritus' theory and said that everything is made of elements. This was believed for over 2,000 years.He studied under Plato from 367 B.C. to 347 B.C.and later tutored Alexander the Great at the Macedonian court from 342 B.C. to 399 B.C. -
370
Democritus
Democritus theorised that everything is made of atoms. -
John Dalton
Daltons 5 postulates(Dalton’s Atomic Theory):
All matter consists of tiny particles.
Atoms are indestructible and unchangeable.
Elements are characterized by the mass of their atoms.
When elements react, their atoms combine in simple, whole number ratios.
When elements react, their atoms sometimes combine in more than one simple, whole number ratio. -
Crooke
the development of a better vacuum pump that allowed him to make cathode-ray tubes with a smaller gas pressure. -
John Newlands
The law of octaves says if the chemical elements are arranged according to increasing atomic weight, the ones that have similar physical and chemical properties happen after each interval of seven elements. -
Mendeleev
He organized the periodic table by the molecular weights of the elements and by their properties. -
Rutherford
descovered the nucleus. known as "Father of Physics" -
JJ Thomson
Descovered the electron -
Bohr
Quantum theory of Matter. Nobel prize
