Niels Bohr

Atomic energy  -   · The energy generated from the splitting of the atom (though nuclear fusion would later add further possibilities).

Bohr atomic model  -   · The Bohr model stabilized Rutherford's original picture by showing that the atom could exist only in discrete energy states.

Complementarity  -   · In light of the indeterminacy set forth by Heisenberg's uncertainty principle, the principle of complementarity argues that two answers are preferable to one when neither is itself complete.

Compound nucleus -   · A temporary excited state of the nucleus that occurs upon the collision of two particles. Bohr postulated that the nucleus might discharge this excess energy through the emission of radiation.

Copenhagen Institute  -   · Founded and headed by Bohr, this Institute soon became the world center for modern physics. Here Bohr cultivated new generations of physicists, while hosting colloquia that would repeatedly alter the course of history.

Correspondence principle -   · This principle states that a new theory must be applicable to all phenomena for which a preceding theory was valid. It applies particularly to theories at the atomic level, which had to be evaluated against traditional phenomena as well, since classical physics had successfully explained it.

Liquid-drop model -   · A theoretical model proposed by Bohr that compares the nucleus to a drop of liquid. This model would later have consequences for the discovery of fission.

Nuclear fission  -   · A nuclear reaction in which the nucleus of an atom, usually uranium, is split into two fragments, leading to the release of a great deal of energy.

Quantum theory -   · A theory that addresses the duality of matter and energy, which have the properties of both particles and waves. In creating his atomic model, Bohr specifically applied Planck's idea that energy consists of discrete packets called quanta.

Stationary state  -   · A state of an atomic system that has a defined energy level associated with it.

Uncertainty principle -   · Formulated by Heisenberg, this principle states that the velocity and position of an electron can never be exactly determined, since the act of measurement necessarily disturbs the conditions.

Aage Bohr -  Bohr's fourth son, who accompanied him to Los Alamos and became his assistant before going on to his own career in theoretical physics.

Christian Bohr -  Bohr's father, who was also a famous physiologist and Copenhagen professor.

Ellen Bohr  -  Bohr's mother.

Harald Bohr -  A beloved brother of Niels, who remained a close companion and confidant throughout their lives. Harald was also a distinguished mathematician.

Margrethe Bohr  -  Bohr's wife.

Albert Einstein -  Greatly admired by Bohr, Einstein was one of Bohr's biggest critics. The two engaged in an endless debate that usually centered on the principle of complementarity. Einstein's early work also contributed to Bohr's atomic model.

Werner Heisenberg  -  Early Copenhagen fellow responsible for the development of quantum mechanics. He became most famous for his uncertainty principle.

Hendrik Kramers  -  Dutch physicist who would be a faithful assistant to Bohr for almost ten years. He was pivotal in the establishment of the Copenhagen Institute, and he remained a close friend for many years, helping Bohr to campaign for international cooperation on atomic policy.

Wolfgang Pauli -  Early Copenhagen fellow whose exclusion principle addressed some of the shortcomings of Bohr's own electron theory.

Max Planck  -  One of the early developers of quantum theory, Planck postulated the existence of quanta, which would influence Bohr's atomic model.

Ernest Rutherford  -  One of Bohr's first mentors, Rutherford gave Bohr the direction he needed early on his career. Bohr's atomic model was also largely a revision of Rutherford's original. The two remained close throughout their lives.

Ernest Schrödinger  -  Showed how electron behavior could be understood in terms of waves. Schrödinger's theory yielded the same mathematical results as Heisenberg's quantum mechanics, though their postulations differed fundamentally.

J. J. Thomson -  Physicist whose work Bohr greatly admired, most known for his discovery of the electron. Bohr went to Cambridge with the hope of working with Thomson, but found him less interested than he had hoped. He gave up on Thomson when the prospect of working with Rutherford arose.