Niels Henrik David Bohr was a Danish physicist, born in Copenhagen on October 7, 1885. He made notable contributions to understanding atomic structure and quantum theory, for which he was awarded the Nobel Prize in Physics in 1922. Bohr established the distinct energy levels of electrons and that electrons rotate in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another in his Bohr model of the atom.
Early Years and Education 
Bohr was born as the second of three children in an upper-middle-class Copenhagen household. Ellen, his mother, was the daughter of a renowned Jewish banker. Christian, his father, became a professor of physiology at the University of Copenhagen and was nominated for the Nobel Prize twice.
Niels’ parents were deeply passionate about their children’s education. Niels was taught at home until he started formal schooling at age 7 at the Gammelholm Grammar School. In 1903, aged 17, Niels graduated from high school. Later that year, he began his studies at the University of Copenhagen. He studied astronomy, chemistry, and mathematics and majored in physics.
He studied under Professor C. Christiansen, a deeply creative and gifted physicist, and earned his master’s degree in physics in 1909 and his doctorate in 1911.
In the fall of 1911, he visited Cambridge, where he benefited from monitoring the experimental work being done in the Cavendish Laboratory under the direction of Sir J.J. Thomson while also pursuing his theoretical research. He was working at Professor Rutherford’s laboratory in Manchester in the spring of 1912.
On August 1, 1912, Bohr married Margrethe Nørlund, and the marriage proved a particularly happy one.
Most notable accomplishments:
Niels Bohr, Werner Heisenberg, and Wolfgang Pauli, three famous twentieth-century physicists, created the Copenhagen interpretation of quantum mechanics between 1925 and 1927. It states that systems at the atomic level lack defined attributes before being measured.
Niels Bohr proposed the notion of complementarity for the first time in 1927, stating that a physical phenomenon presents itself differently on the atomic level depending on the experimental apparatus employed to detect it. As a result, light appears as both waves and particles. In 1927, stating that a physical phenomenon presents itself differently on the atomic level depending on the experimental apparatus employed to detect it. As a result, light appears at times as both waves and particles. Wave-particle duality is an example of a complimentary property.
Bohr developed his own renowned Bohr model of the atom by applying Max Planck’s quantum theory to the Rutherford model. The structure of the Bohr model was comparable to that of a solar system, with electrons in set orbits around the positively charged atomic nucleus. Although the Bohr model has been supplanted, its core ideas remain true, and its simplicity makes it appealing.
Societal Impacts-
During the Nazi occupation of Denmark during WWII, Bohr fled to Sweden and spent the final two years of the war in England and America, where he got involved with the Atomic Energy Project. In his later years, he focused on the benign applications of atomic physics as well as the political issues raised by the development of nuclear weapons. He urged for greater openness between nations. His opinions are particularly expressed in his Open Letter to the United Nations, dated June 9, 1950.
Niels Bohr was President of the Royal Danish Academy of Sciences, Chairman of the Danish Cancer Committee, and Vice Chairman of the Danish Atomic Energy Commission.
Among Professor Bohr’s various writings, three volumes in English may be listed here as reflecting his main ideas: The Theory of Spectra and Atomic Constitution, Atomic Theory and the Description of Nature, and The Unity of Knowledge.
Text References-
https://www.famousscientists.org/niels-bohr/
https://www.britannica.com/biography/Niels-Bohr
Image reference-