Notes

democritus he was around 460 -370 bc
proposed an atomic (along with his mentor hich state ment that are small hard an
antoine lavoisier makes a substanial numbers chemisty
john dalson proposed his atomic theory in 1803.all substances are made of atoms atoms are small
Ernest Rutherford, 1st Baron Rutherford of Nelson, OM, FRS[2] (30 August 1871 – 19 October 1937) was a New Zealand-born British physicist who came to be known as the father of nuclear physics.[3] Encyclopædia Britannica considers him to be the greatest experimentalist since Michael Faraday (1791–1867).[3]

In early work, Rutherford discovered the concept of radioactive half-life, proved that radioactivity involved the nuclear transmutation of one chemical element to another, and also differentiated and named alpha and beta radiation.[4] This work was performed at McGilNiels Henrik David Bohr (Danish: [nels ˈboɐ̯ˀ]; 7 October 1885 – 18 November 1962) was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was also a philosopher and a promoter of scientific research.

Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid. He conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr's thinking in both science and philosophy.

Bohr founded the Institute of Theoretical Physics at the University of Copenhagen, now known as the Niels Bohr Institute, which opened in 1920. Bohr mentored and collaborated with physicists including Hans Kramers, Oskar Klein, George de Hevesy, and Werner Heisenberg. He predicted the existence of a new zirconium-like element, which was named hafnium, after the Latin name for Copenhagen, where it was discovered. Later, the element bohrium was named after him.

During the 1930s, Bohr helped refugees from Nazism. After Denmark was occupied by the Germans, he had a famous meeting with Heisenberg, who had become the head of the German nuclear weapon project. In September 1943, word reached Bohr that he was about to be arrested by the Germans, and he fled to Sweden. From there. erwin scahrodinger in 1926 he futher explained the nature of electrons inan atom.