(1900-1915)

**__1900-1915__

Niels Bohr** (7 October 1885 ( 1885-10-07 ) -18 November 1962) Denmark Bohr was born in Copenhagen, Denmark. His father was a devout Lutheran and a physiology professor at the University of Copenhagen. His brother was a mathematician and played football in the Olympics. He studied under Ernest Rutherford at the University of Manchester. He had six sons with his wife Margrethe Bohr. One of his children died in a boat accident and another died due to childhood meningitis. Bohr contributed the Bohr model of atomic structure, the theory that electrons travel in orbits, and the theory that the electrons in the outer orbit determined the chemical properties. He also theorized that higher-energy orbits could drop to lower-energy orbits, emitting a photon. This became the basis for quantum theory.

( 7 November 1867 - 4 July 1934) Poland Curie was born in Warsaw, Poland. She was the fifth and youngest child. Her grandfather had been a respected teacher in Lublin. Her father taught mathematics and physics. When she was 10 years old she started attending boarding school. Her family on her mother and father’s side lost all their belonging in patriotic uprisings causing Curie much difficulty. She studied at the Sorbonne in Paris. Curie said that there were some atoms there were more active than uranium. She used an electrometer to measure the material for electrical charge. She discovered that radioactive samples caused the air around them to conduct electricity. She found that uranium compound’s activity depended solely on the amount of uranium and nothing else. She also discovered that pitchblende and torbernite were more active than
 * Marie Curie **

 (22 March 1868 – 19 December 1953) United States Millikan received his bachelor’s degree in the classics and his doctorate in physics from Columbia University. He received the Nobel laureate for his works in physics. He served as President of Caltech from 1921 to 1945. Millikan did an experiment to show the charge or an electron. He used an oil-drop experiment to prove his idea. His experiment helped prove that there were subatomic particles. His experiment, while great at its intended purpose, also allowed a hands-on way to prove that charge is quantized.
 * Robert A. Millikan **