Aristotle
Early Greek Theories
•400 B.C. - Democritus thought matter could not be divided indefinitely.
•350 B.C - Aristotle modified an earlier theory that matter was made of four “elements”: earth, fire, water, air.
Democritus
•Aristotle was wrong. However, his theory persisted for 2000 years.
fire
air
water
earth
•This led to the idea of atoms in a void.
กำลังโหลด…
John Dalton
•1800 -Dalton proposed a modern atomic model
based on experimentation not on pure reason.
•All matter is made of atoms.
•Atoms of an element are identical.
•Each element has different atoms.
•Atoms of different elements combine in constant ratios to form compounds.
•Atoms are rearranged in reactions.
•His ideas account for the law of conservation of mass (atoms are neither created nor destroyed) and the law of constant composition (elements combine in fixed ratios).