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The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Atomic theory is the scientific theory that matter is composed of particles called atoms. The definition of the word "atom" has changed over the years in response to scientific discoveries.
The Rutherford model is a name for the first model of an atom with a compact nucleus. The concept arose from Ernest Rutherford discovery of the nucleus. Rutherford directed the Geiger–Marsden experiment in 1909, which showed much more alpha particle recoil than J. J. Thomson's plum pudding model of the atom could explain. Thomson's model had ...
The expedition ship RRS Discovery in the Antarctic alongside the Great Ice Barrier, now known as the Ross Ice Shelf. The Discovery Expedition of 1901–1904, known officially as the British National Antarctic Expedition, was the first official British exploration of the Antarctic regions since the voyage of James Clark Ross sixty years earlier (1839–1843).
The Bohr model of the atom, with an electron making instantaneous "quantum leaps" from one orbit to another with gain or loss of energy. This model of electrons in orbits is obsolete. A problem in classical mechanics is that an accelerating charged particle radiates electromagnetic radiation, causing the particle to lose kinetic energy.
The meaning of the preceding definition is as follows. The caesium atom has a ground state electron state with configuration [Xe] 6s 1 and, consequently, atomic term symbol 2 S 1/2. This means that there is one unpaired electron and the total electron spin of the atom is 1/2. Moreover, the nucleus of caesium-133 has a nuclear spin equal to 7/2.
In October 1913, a close friend of Captain Scott, Joseph Foster Stackhouse, announced plans for a British Antarctic Expedition to explore the uncharted coastlines between King Edward VII Land and Graham Land. The expedition was due to depart England in August 1914 aboard RRS Discovery, the ship of Crean's first mission to Antarctica. In ...
Part of the planning for the expedition had provided for a relief ship to follow a year later, in case Discovery was lost in the Antarctic; on reading a newspaper article about this some months later, Evans saw an opportunity for adventure and wrote to Sir Clements Markham, the organising force behind the expedition. He met Markham twice in the ...
In atomic physics, the Bohr model or Rutherford–Bohr model was the first successful model of the atom. Developed from 1911 to 1918 by Niels Bohr and building on Ernest Rutherford 's nuclear model , it supplanted the plum pudding model of J J Thomson only to be replaced by the quantum atomic model in the 1920s.