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Leucippus was the first Western philosopher to develop the concept of atoms, but his ideas only bear a superficial resemblance to modern atomic theory. Leucippus's atoms come in infinitely many forms and exist in constant motion, creating a deterministic world in which everything is
Dalton thought that water was a "binary compound", i.e. one hydrogen atom and one oxygen atom. Dalton did not know that in their natural gaseous state, the ultimate particles of oxygen, nitrogen, and hydrogen exist in pairs (O 2, N 2, and H 2). Nor was he aware of valencies. These properties of atoms were discovered later in the 19th century.
Democritus (/ d ɪ ˈ m ɒ k r ɪ t ə s /, dim-OCK-rit-əs; Greek: Δημόκριτος, Dēmókritos, meaning "chosen of the people"; c. 460 – c. 370 BC) was an Ancient Greek pre-Socratic philosopher from Abdera, primarily remembered today for his formulation of an atomic theory of the universe. [2] Democritus wrote extensively on a wide ...
Democritus and Lucretius denied the impossibility of a vacuum, being of the opinion that there must be a vacuum between the discrete particles (atoms) of which, they thought, all matter is composed. In general, however, the belief that a vacuum is impossible was almost universally held until the end of the sixteenth century. [ 41 ] ...
The two discovering parties independently assign the discovered meson two different symbols, J and ψ; thus, it becomes formally known as the J/ψ meson. The discovery finally convinces the physics community of the quark model's validity. 1974 Robert J. Buenker and Sigrid D. Peyerimhoff introduce the multireference configuration interaction method.
The electron cloud is a region inside the potential well where each electron forms a type of three-dimensional standing wave—a wave form that does not move relative to the nucleus. This behavior is defined by an atomic orbital , a mathematical function that characterises the probability that an electron appears to be at a particular location ...
The successes of kinetic theory gave further credence to the idea that matter is composed of atoms, yet the theory also had shortcomings that would only be resolved by the development of quantum mechanics. [6] The existence of atoms was not universally accepted among physicists or chemists; Ernst Mach, for example, was a staunch anti-atomist. [7]
Any electron beam would collide with some residual gas atoms within the Crookes tube, thereby ionizing them and producing electrons and ions in the tube (space charge); in previous experiments this space charge electrically screened the externally applied electric field. However, in Thomson's Crookes tube the density of residual atoms was so ...