Section 2.1 The History of Chemistry
Ideas About the Composition of Matter The idea that all matter is made up of particles started with Greek Philosopher more than 2500 years ago. How many times can you break down a substance until it cant be broken down any more?
Democritus atomos = “uncuttable” The smallest particle that cannot be broken down any more Each material is made up of different types of matter
Aristotle Earth Air Fire Water He supported a different hypothesis, everything is made up of four elements… Earth Air Fire Water
Alchemy Part magician part scientist
Alchemists tried to turn lead to gold
Modern Chemistry
Daltons Theory Each element is made of an atom. Atoms of one element are identical. These atoms all the same mass. No two elements have atoms with the same mass. Billiard ball model atoms are like tiny solid spheres.
Adding electrons…
J.J Thompson discovered the electron. The raisin bun model
Rutherford’s planetary model (1907) nucleus (+) electron (-)
The atom is made up of mostly SPACE
Chadwick nucleus (+) containing protons (+) and neutrons (=) electron (-)
Bohr Model (1922) Electron Shells
Quantum Mechanical Model – todays model
Which model of the atom will we use? nucleus protons (+) neutrons (=) electron (-)