The Evolution of our Atomic Theory

Ancient Greece to Present Day

•Ancient Greek philosopher•Coined the term atom(from the greek atomos-indivisible)•Matter is made up of small particles

that cannot be divided•Atoms differed in size and shape and were able to combine in different combinations

•Experimented with gases•Published his atomic theory in 1808•6 Important Points:•Different elements have different atoms• Atoms of one element are identical•Different elements have different properties• Atoms are rearranged by chemical reactions• Atoms combine to form compounds• Compounds have definite types, numbers and

proportions of elements•Father of Modern Chemistry

•English Physicist and Chemist•Identified the electron as having a negative charge•Atoms are neutral•Electrons are embedded in a positive sphere•Chocolate Chip Cookie Dough Model

•Gold Foil Experiment•Bombarded Gold foil with Alpha

particles(positively charged lightweight atoms)•Some went straight through, while some

bounced backwards•Showed atom is made of empty space and a

strong positive center(THE NUCLEUS!)•Electrons were located around the nucleus,

but he didn’t know where

Rutherford Experiment Video

•Danish Physicist•Used Rutherford’s results to describe location of electrons•Electrons move around nucleus in fixed orbits(orbitals)

•Still used today to describe atom

•Combination of de Broglie and Schrodinger’s ideas•Shows that electrons have a certain probability to be in specific energy levels(orbitals)•Chadwick later discovered the third sub-atomic particle•The neutron—neutral charge