ATOMS

DEMOCRITUS 400 B.C.

ATOMOS THEORY

• First person to come up with the idea of Atomos
• Atomos Model: The atom is indivisible
• Created in 465 B.C.

ATOMOS MODEL

• Atoms cannot be divided or cut
• All matter is composed of tiny, individual particles
• Atoms are infinite in number and always moving

ARISTOTLE 384 B.C.

EARTH WIND FIRE WATER THEORY

• Aristotle had in five elements: Earth, Wind, Fire, Water, and Aether
• He believed in Aether because the other four elements couldn't make stars
• Aristotle also believed that each element could transform into the other

EARTH WIND FIRE WATER THEORY

• His theory lasted over 2000 years
• He had acquired this theory from his mentor
• He was also opposed Democritus' theory

DALTON 1803

ATOMIC THEORY

• Each element is composed of small atoms
• All atoms in the element are identical, but different from other elements
• Atoms are not created or destroyed
• A compound has the same relative numbers and kinds of atoms

BILLARD BALL MODEL

• Atoms make up matter
• Different elements make up a compound
• To seperate or combine elements form a chemical reaction
• Model looked like one large ball that represented an atom

THOMSON 1897

CATHODE RAY

• Its particles carry a negative charge
• Lead to the discovery of electrons
• Model was a tube with a hole on each sice

PLUM PUDDING MODEL

• Tiny, negatively charged electrons embedded in a positively charged substate
• The electrons were believed to have balanced the positive charge
• Generally accepted by society
• It is like raisins inside a large bowl of plum pudding

RUTHERFORD 1899

GOLD FOIL EXPERIMENT

• Proved Thomson wrong about electrons
• Particles bounce off the foil into the screen, admitting radiation
• Looks like a movie projector onto a screen

POSITIVELY CHARGED NUCLEUS MODEL

• The electrons rotate around the positively charged Nucleus
• Similar to planets orbiting the sun
• High charge concentration in Nucleus

MILLIKAN 1909

OIL DROP EXPERIMENT

• Measured the charge of an electron
• Like spraying rat poison into a rat nest
• An electron is 2000 times lighter than an atom of hydrogen

MASS/CHARGE OF ELECTRON

• One drop of oil had an infinite vslue of electrons
• It proved that they were the lightest particle
• Also proved Thomson's hypothesis correct

CHADWICK 1932

DISCOVERY OF NEUTRON

• Chadwick discovered the Neutron in 1932 when unknown radiation came out of a Parrafin
• A Neutron has no electrical charge
• The Neutron was not attached to the Nucleus