Niels Hedrik David Bohr
Niels Hendrik David Bohr was one of the foremost scientists of the 20th century. The Nobel prizewinning physicist was known for his development of the theory of atomic fission that led to the development of the atomic bomb.
He was born on Oct. 7, 1885, in Copenhagen, Denmark. His father, Christian, was a professor at the University of Copenhagen and his brother, Harold, was a great mathematician. Bohr and his family grew up in an atmosphere that helped the development of his knowledge. His father was largely responsible for awakening his interest in physics while, his mother came from a family well known in the field of education. After Gammelholm Grammar School in 1903, he entered Copenhagen University where He won a gold medal from the Royal Danish Academy of Sciences for his theoretical analysis of vibrations of water jets as a means of determining surface tension. He received his Master's degree from the University of Copenhagen in 1909 and his doctorate in 1911 with a thesis Studies on the electron theory of metals. Bohr went to England to study with Sir J.J. Thomson at Cambridge. He had intended to spend his entire study period in Cambridge but he did not get on well with Thomson so, after a meeting with Ernest Rutherford in Cambridge in December 1911, Bohr moved to Manchester in 1912. There he worked with Rutherford's group on the structure of the atom. Rutherford became Bohr's role model both for his personal and scientific qualities. Using quantum ideas due to Planck and Einstein, Bohr conjectured that an atom could exist only in a discrete set of stable energy states.
Bohr won the Nobel piece prize for his theory of atomic structures. According to Microsoft Encarta His work drew on Rutherford’s nuclear model of the atom, in which the atom is seen as a compact nucleus surrounded by a swarm of much lighter electrons. He thought that electrons are arranged in definite shells, or quantum levels, at a big distance from the nucleus. The arrangement of these electrons is called the electron configuration. The number of these electrons equals the atomic number if the atom; hydrogen has a single electron, helium has 2, and uranium has 92. The electron shells are built from a first shell to a total of seven shells. The first shell is complete with two electrons, the second can hold up to eight electrons, and the following shells hold larger numbers. The last electrons determine the chemical behavior of the atom