What is Modern Atomic Theory?June 26, 2021
1803-> John Dalton (1766 – 1844), the son of a weaver and one of the professors of the Nonconformist New College in Manchester, brought up the atomic concept put forward by Democritus and Leucippus in the early 19th century. Dalton’s atomic theory consists of 3 items:
Every element is made up of very small and indivisible particles called atoms. Atoms cannot be formed or divided in chemical reactions.
All atoms of an element have the same mass, weight and other properties. But atoms of one element are different from atoms of all other elements.
A chemical compound is formed by combining two or more elements in a simple numerical ratio.
A + B ⇒ AB and A + 2B ⇒ AB2
In addition, Dalton calculated the relative weights of 20 elements (hydrogen, nitrogen, carbon, oxygen, phosphorus, sulfur, magnesium …) and published it. Thus, the theory of the 4 elements, which passed from Greek thought to Christianity, was completely destroyed. It has already been proven that soil, water, air and fire are not elements, with the contribution of many scientists. Dalton made a new element definition and completely buried this old element concept into history.
1897 ⇒ On this date, the British scientist John Joseph Thomson (1856-1940) observed that there are particles lighter than the lightest known atom. He called them ‘corpuscles’. Today we call these particles ‘electrons’.
1911 ⇒ On this date, Thomson’s student Ernest Rutherford (1871-1937) proposed a new model of the atom based on experiments with positively charged alpha particles striking a gold plate. Accordingly, most of the atomic mass is concentrated in the nucleus behind it, and electrons revolve around this nucleus.
1912 ⇒ In 1912, a year after Rutherford proposed his own model of the atom, Danish physicist Niels Bohr (1885-1962) came up with his own model of the atom. Accordingly, there is a positively charged nucleus and electrons around it, but these electrons were rotating in certain orbits. These orbitals can be determined according to the energy of the electron.
1927 ⇒ Atomic theories continued to diversify and to develop old theories after 1912. Today, the development continues at full speed. But the most important among them is Werner Carl Heisenberg’s (1901-1976) introduction of the uncertainty principle. The importance of this principle is that it revolutionized world views as well as physics. According to this principle, if the moment of a subatomic particle is known, an uncertainty appropriate to the state of the particle must also be found.
Compiled by: Sociologist Ömer YILDIRIM
Source: Atatürk University Department of Sociology Lecture Notes for Grade 1 “Introduction to Philosophy” and Grade 3 “History of Contemporary Philosophy” (Ömer YILDIRIM); Open Education Philosophy Textbook