UP AND ATOM It’s time for… THE HISTORY OF THE ATOM !

Democritus (400 B.C.) First person to propose that matter is made of about 100 tiny particles called atoms that collide and combine to make everything. His theory was not widely believed, even though it turned out to be correct. Like other scientists of his time, he had no real evidence for his ideas.

Aristotle -- 350 B.C. FIRE WATER EARTH AIR Denied the existence of atoms. Said matter consisted of combinations of only four elements -- air, earth, fire, and water. Was widely respected, and his ideas formed the basis of science for nearly 2000 years. Lead to alchemy and superstition. FIRE AIR EARTH WATER

The Dark Ages of Chemistry 400 B.C. - 1600 A.D. The Dark Ages of Chemistry The idea of atoms was lost

Robert Boyle 1661 Renews belief in the idea of atoms through his experiments with gases

Conservation of Matter Antoine Lavosier 1780 Modern Chemistry Father of Modern Chemistry Antoine Developed the theory of Conservation of Matter

John Dalton --1800 (a.k.a “the marble guy”) Atoms are all solid with uniform density Atoms are the smallest particles of nature All atoms of the same element are identical Atoms of different sizes can combine to form compounds An atom (Close-up view)

Discovers a negatively charged beam in an electrified vacuum tube. 1879 William Crookes Discovers a negatively charged beam in an electrified vacuum tube.

Proved that Crookes’ negative “beam” was really particles he called “electrons”. Realized that these electrons must be smaller than the atom Developed the “Plum Pudding” model of the atom First person to realize that atoms are made of small parts J.J. Thomson 1897

What is plum pudding? I prefer mint chocolate Chip ice cream Atoms are negative electrons stuck in a positive glob

Ernest Rutherford - 1911 Performed Gold Foil Experiment Won Nobel Prize for Chemistry

The Gold Foil Experiment Bombard thin piece of gold foil with alpha particles Result: a few are deflected while most are unaffected What does it all mean?

What Happened?

What Does it Mean? Atoms have dense area in the middle The nucleus The proton Electrons travel around away from the nucleus The atom is mostly empty space

NIELS BOHR 1913 Was a friend of Einstein Developed important ideas of quantum physics and atomic structure Use light spectrum to explain the structure of the atom

Light Spectrum

Niels Bohr Compares electrons orbiting the nucleus of an atom to planets orbiting around the sun. Electrons occupy distinct orbitals. Orbitals have certain energies and distances from the nucleus.

Erwin Schrodinger Regions where electrons are most likely found are called “electron clouds”. Different types of orbitals have different shapes and different levels of energy. Although difficult to understand, the results were spectacular! This new model of the atom explained the physical properties of atoms, and the Periodic Table, perfectly.

Discovered the neutron James Chadwick 1932 Discovered the neutron neutron Predicted by Rutherford in1920, but very difficult to detect. New tool for probing and changing the nucleus of an atom.

1980’s The first atoms are seen with scanning tunneling microscopes

1995 Fermi lab scientists in Batavia, Illinois study and detect six types Of quarks Quarks are particles believed to Make up protons and neutrons