Leucippus
-Greek Philosopher
-Could matter be divided into smaller pieces
-Thought smallest pieces were indivisible
Democritus
-Greek Philosopher
-“atomos” (indivisible)
-Thought there were different types of atoms (size/shape) - substances composed of mixtures of atoms
Aristotle
-opposed idea of atomism -couldn’t believe matter couldn’t be further separated
-promoted though that matter made of 4 elements
Lucretius
-Roman Poet
-“On the Nature of Things” -explained and preserved atomistic view
Johann Gutenberg
-German inventor
-invented printing press
-Lucretius’ poem was one of earliest books to appear -spread idea of atomism around the world
Robert Boyle
-Irish chemist -experimented with gases
-began process of experimentation
-Applied exact measurements to experiments
Antoine Lavoisier
-French Chemist
-Performed experiments with very accurate mass
-Discovered Law of Conservation of Mass
-“FATHER OF MODERN CHEMISTRY”
Joseph Proust
-French Chemist
-conducted careful experiments
-Law of Definite Proportions
John Dalton
-English chemist and school teacher
-Law of Multiple Proportions
-The atomic theory
Law of Conservation of mass
mass cannot be created/destroyed by ordinary mean
Law of Definite Proportions
a chemical compound contains the same elements in same proportion by mass regardless of the size/source of the sample
Law of Multiple Proportions
if 2 or more compounds are composed of the same elements, those elements combine in different whole # ratios (by mass) to yield different compounds
What 3 parts of Dalton’s Atomic Theory remain unchanged today?
-All matter is composed of atoms
- Atoms of different elements can combine in simple, whole # ratios to form chemical compounds
-In chemical reactions, atoms are combined/separated/rearranged
What 2 parts of Dalton’s Atomic Theory where modified and what are they now?
- Atoms of a given element are identical in size, mass, and other properties
-(can have different masses-isotopes have different # of neutrons)
-Atoms cannot be created/subdivided/destroyed
-(can be done using nuclear chemistry)
Alessandro Volta
-Italian Physicist
-invented first electrical battery
-produced first electrical current
-proved water wasn’t element using electrolysis of H2O (determined 2:1 ratio)
William Crookes
-Crookes Tube; evacuated glass tube w/ metal electrodes that sealed inside
-determined that ray went from the cathode to the anode (a cathode ray tube)
J.J Thomson
-English Physicist
-Studied Cathode Ray Tube; DISCOVERED ELECTRON
-Led to Plum Pudding Model
Plum Pudding Model(Raisin pudding model)
negative electrons surrounded by positive gel-like substance
Robert Millikan
-American Physicist
-Oil Drop Experiment
-measured min electric charge that could be carried by a particle (charge of an electron)
-enabled him to find mass of electron
Ernest Rutherford
-J.J. Thomson student
-worked w/ nuclear radiation
-Gold Foil Experiment; DISCOVERED NUCLEUS & PROTONS
Gold Foil Experiment
1) Atom mostly made of empty space
-most particles went through foil
2) Atom has a positive, small, dense nucleus
- positive particles repelled
-only few repelled;most went through
-positive particles BOUNCED back
James Chadwick
-discovered neutron
- instead became famous physicist (wanted to be mathematician)
Avogadro’s Law
at a fixed temperature and pressure, equal volumes of gases contain the same # of molecules
Avogadro’s Number
6.022 x 10’23 = 1 mole
