History OF Matter AND Atoms PDF

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- HISTORY OF MATTER AND ATOMS
- SCIENTISTS WHO CONTRIBUTED IN THE HISTORY OF MATTER AND ATOMS...

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HISTORY OF MATTER AND ATOMS SCIENTISTS WHO CONTRIBUTED IN THE HISTORY OF MATTER AND ATOMS 1. EMPEDOCLES - (450 BC) all things = 4 primal elements: earth, air, fire and water 2. DEMOCRITUS - (400 BC) all matter = made up of small particles  atoms - Atoms cannot be divided into smaller units - Believed that there is a 5th element  ether 3. ARISTOTLE - (380-320 BC) Matter was continuous - Can be further divided into smaller pieces 4. JOSEPH PROUST - Law of definite proportions - “When forming a compound, elements always combine in similar proportions by mass regardless of the size of the sample” 5. JOHN DALTON - English teacher - (1808) Atomic theory - Law of Multiple Proportions - “When 2 elements combine with each other to form 2 or more compounds, the ratios of the masses of 1 element that combines with the fixed mass of the other are simple whole numbers.” 6. DMITRY MENDELEEV - (1869) Arranged the periodic table based on their atomic mass 7. ANTOINE BECQUEREL and MARIE CURIE - (1890s) Radioactivity = causes atoms to break down 8. WILHELM RÖNTGEN - (1895) X rays 9. JOSEPH JOHN THOMSON - (1897) Electrons - (1904) Plum pudding model of atom 10. ROBERT MILLIKAN - (1908-1917) Found that the charge of an electron is equal to -1.6022 x 10^-19 C

11. ERNEST RUTHERFORD - (1910-1911) Atoms are mostly empty space - Gold foil experiment 12. NIELS BOHR - (1913) Proposed atomic model - Shows electrons move in concentric orbits around the nucleus 13. HENRY MOSELEY - (1913) Used x-ray spectra to study atomic structure - Helped discover the atomic number of each element 14. ERNEST RUTHERFORD - (1919) Protons 15. JAMES CHADWICK - (1932) Neutrons 16. ROBERT BOYLE - First modern chemist...