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458 BCE
Democritus
Birth : around 460 BCE
Death : around 370 BCE -
431 BCE
World Event - Peloponnesian War
The Peloponnesian War started in 431 BC and ended on April 25, 404 BC. The war was in ancient Greece and was fought between the most powerful city states at the time, Athens and Sparta. This war lasted 15 years but Sparta came out of the war victorious. -
400 BCE
Democritus Discovers the Atom.
Around 400 BCE the Greek philosopher Democritus Introduces the idea of the atom. Democritus introduced the idea that matter was subdivided into indivisible and immutable particles that created the appearance of change when they joined and separated from others. Democritus said that atoms are the basic building blocks of matter, Democritus thought that atoms are tiny, uncuttable, solid particles that are surrounded by empty space and are constantly moving. -
John Dalton
Birth : September 6th in 1766.
Death : July 27 in 1844 (77 years old) -
World Event - Revolutionary War
Start : April 19th 1775
End : September 3rd, 1783
Outcome : United States won
The Revolutionary war was between 13 of Great Britain's North American colonies, They fought to throw off British rule to and to establish a break from the monarch. The 13 colonies wanted to be sperate from Britain as they just founded the Declaration of Independence in 1776. The War started on April 19th 1775 and lasted until September 3rd, 1783. The United States were victorious granting the US freedom from Britain. -
Michael Faraday
Birth : September 22nd 1791.
Death : August 25th 1867 (75 years old)
Faraday contributes to the discovery of the atom and the atomic theory because he was the first to figure out that atoms have an electrical component. He discovered this when studying properties and reactions of electrolysis, which runs an electrical current through water or other liquids. -
John Dalton's "Marble Model"
In 1803 the scientist John Dalton came up with the theory that suggested that all matter is composed of indivisible and indestructible atoms with distinct masses and properties. He discovered this through endless experiments. This discovery helped assign atomic weights to the 20 elements that Dalton knew of at the time. -
James Chadwick
Birth : October 20, 1891
Death : July 24, 1974 (84 years old ) -
Eugen Goldstein
Birth : September 5th 1850
Death : December 25th 1930 (80 years old)
Eugen Goldstein was a German physicist who was responsible for the discovery of positive ions. Goldstein discovered this by experimenting with a cathode ray tube with holes in the cathode. While he was using it he noticed that there were rays traveling in the opposite direction from the cathode rays. He realized that these were positive ions. -
JJ Thomson
Birth : December 18, 1856
Death : August 30, 1940 (age 83 years) -
Ernest Rutherford
Birth : August 30, 1871
Death : October 19, 1937 (66 years old) -
Neils Bohr
Birth : October 7, 1885
Death : November 18, 1962 (77 years old) -
Edwin Schroedinger
Birth: August 12, 1887
Death : January 4, 1961 (73 years old) -
JJ Thompsons "Plum Pudding Model"
JJ Thompson was famous for his discovery of the electron in 1898 Thompson discovered the electron and then went on to propose a model for the structure of the atom. He discovered the proton through many experiments with cathode ray tubes that showed that all atoms contain tiny negatively charged subatomic particles or electrons. Thompson thought the atom was negatively charged because the electrons stuck within a positively charged base. -
World Event - The Treaty of Paris (1898)
The Treaty of Paris was a treaty that was signed on December 10th 1898 ending the Spanish-American War. Back on April 25, 1898 the United States declared war on Spain because of the sinking of the battleship Maine in Havana harbor on February 15, 1898. The war lasted a total of 100 days and had only a few battles, But the treaty guaranteed that Spain had to give Guam and Puerto Rico to the United States. -
Robert Millikan
Birth : March 22nd, 1868
Death : December 19th, 1953 (85 years old)
Discover : 1910
Robert Millikan was an American physician and in 1910, Millikan discovered the charge of an individual electron. He did this through an experiment that determined the charge. He would suspend oil droplets between two electric plates and determine their charges. Once the oil dropped a fine mist fell through a hole in the upper plate. From their velocity, he could calculate the mass of each drop. -
Ernest Rutherford “Nuclear” Model
Rutherford discovered the nuclear structure of the atom. He found alpha rays in the atom structure. The way that he discovered the structure was using gold foil. He fired a beam of particles at the gold foil. Most of the alpha particles passed through the foil, but a few bounced backwards. This showed that most of the atom is made up of empty space surrounding a tiny nucleus. He concluded that an atom is a small dense positively charged nucleus, with small electrons moving around the nucleus -
World Event - Woodrow Wilson Presidency
Birth : December 28, 1856
Death : February 3, 1924
Thomas Woodrow Wilson (December 28, 1856 – February 3, 1924) was the 28th president of the United States, serving from 1913 to 1921. He served as a democrat. His vice president was Thomas R. Marshall who served as the 28th vice president. -
Neils Bohr “Solar System” Model
Neils Bohr was a Danish physicist who helped understand the atomic structure. He proposed a model of the atom in which the electron was only in certain orbits around the nucleus. He concluded that the electrons move at fixed distances around the nucleus. -
Edwin Schroedinger “Electron Cloud” Model
Idea Published : 1926
Edwin Schrodinger was an Austrian theoretical physicist who contributed to the wave theory of matter. Schrodinger developed math equations to describe the motions of how electrons move in the atom. He used his work to make the “Electron Cloud Model”. In 1926 Schrodinger published a wave equation that accurately calculated the energy levels of electrons in atoms. -
Werner Heisenberg
Birth : December 5, 1901
Death : February 1, 1976 (74 years old)
Theory published : February 1927
Werner Heisenberg was a German theoretical physicist who helped contribute to the atom theory by coming up with a formula that says that a particle's position and momentum cannot be known exactly. He did this by using quantum mechanics and matrices which is how he discovered the uncertainty principle. -
World Event - Wall Street Stock Market Crash
Date : October 24, 1929
The Stock Market crash happened on October 24th 1929. This is also called black Thursday, because 12.9 million shares were traded in the stock exchange in a single day compared to the normal amount of 4 million. This Crash is what kicked off the Great Depression because everyone lost money, including businesses who eventually had to close. -
James Chadwick “Electron Cloud” Model with Neutrons
James Chadwick was an english physicist who is best known for his discovery of the neutron in 1932. The way Chadwick discovered this was through performing a beryllium bombardment experiment by himself and found out that radiation is being composed of particles of mass approximately equal a proton but without the electrical charge therefore being called “neutrons” -
World Event - Amelia Earhart
On May 22, 1932 Amelia Earhart, otherwise known as the Queen of the Air, was the first woman to fly alone over the Atlantic Ocean. Earhart started her flight in Canada, and landed about 15 hours later near Londonderry, Northern Ireland. Earhart's bigger goal was to become the first person to circumnavigate the globe around the equator, but unfortunately her 1935 Lockheed Electra 10-E plane ran out of fuel and crashed somewhere in the Pacific Ocean, the location of the crash is still unknown.