Contributions to the Atomic Theory

Alchemists
european scientists, 800-900 years ago, in Europe, developed into what is now modern chemistry, started to catalog elements, tried to change ordinary metals in to gold

Democritus
ancient greek philosopher; everything is made of atoms; can’t be created, destroyed, or divided, between atoms is empty space; coined the term atomus

John Dalton
first explanation of matter and it properties; based his theory on the law of conservation of mass

Joseph Proust
proposed the law of definite proportions;

Antoine Lavosier
considered father of modern chemistry; named oxygen; proposed the law of conservation of mass

Dalton’s experiment
did experiments on gases to see if individual gases had an effect on the mixtures as a whole

Dalton’s Theory
– Elements are made of atoms
-all atoms of a given element are identical
– atoms are indivisible in chemical processes
– the atom in one element is unique than another
-elements can be combined to form compounds that have the number and types of atoms

J.J. Thomson
-still believed the atom was solid
– discovered the electron (neg. charge)
– concluded also that the atom must have a positive particle to balance the negative
-tried to determine the mass of a cathode ray particle
PLUM PUDDING

Thomson’s experiment
-Used cathode and anode to determine some particles have a negative charge;
-had a machine which seperated positive and negative electrons in any gas
Thomson's experiment

Max Plank
quantum theory; only certain amounts of energy can be emitted; suggests nature has forbiddens and allowables;

Robert Millikan
measured the charge and mass of an electron; mass is at least 1000 times smaller than the lightest atom

Millikan’s experiment
oil drop experiment; let a single oil drop fall, using the electric field of an electron he would try to suspend the drop and keep it from falling
Millikan's experiment

Ernest Rutherford
nuclear atom that has a positively charged dense center called a nucleus; concluded that the nucleus contained protons; proved the plum pudding model incorrect

Rutherford’s experiment
conducted to see if alpha particles would pass though; large angles ended up being produced by different particles
Rutherford's experiment

James Chadwick
discovered the neutron

Niels Bohr
electrons move in 7 orbitals around nucleus; improved Rutherford’s model; electrons can never be in between energy levels, but can jump from each one

Curies
discovered and studied radium and polonium; measured power of ionization

Henry Moseley
used self-built equipment to prove every element’s identity is unique due to the number of protons present; RECREATED PERIODIC TABLE;

Henri Becquerel
discovered radioactivity; found 3 types of particles using x-rays

Becquerel’s experiment
believed uranium absorbed energy from the sun; exposed uranium to the sun covered in black paper, even though it was a cloudy day the paper still had traces of uranium; uranium gave off radiation

Max Planck
originated quantum theory of energy

Louis de Broglie
discovered the wave nature of electrons and suggested that all matter has wave properties; electrons have a dual particle wave nature

Erwin Schrodinger
modernized Louis de Broglie’s wave equation by explaining that an atom would move as a wave; created the quantum mechanical theorem; ELECTRON CLOUD MODEL

Albert Einstein
developed the theory of relativity, which states that time, space, and mass are relative to each other and not fixed.

Michael Faraday
proved that atoms were held together by electrical components; proposed the electromagnetic theory of light;

Faraday’s experiment
created the first electromagnet using a coil wrapped around a paper cylinder with wire and connected to a galvanometer, then moved a magnet back and forth inside the cylinder