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History of Atomic Theory Timeline Project

Apr 1, 2019 at History Essays

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Development of atomic theory represents essential contribution to physical science and background of different scientific provisions. Significant historic advancement paved the way to current level of atomic knowledge. Research works of the authors of different epochs conform the interest of this scientific topic and its deep subsequent examination. It took whole decades for scientists to discover an atom and its structure. Influencing factors included social, political, economic, technical, and technological aspects of science improvement and human development. Nevertheless, the development of atomic theory was related to the advancements of previous generations of scientist’s and the degree of their progress in the examination of atom. Scientific discoveries made indispensable individual endowments to current understanding of the atomic structure and the provisions of the atomic theory.

Historical Stages of Atomic Theory

Atomic theory is based on the valid assumption that each thing consists of atoms as the smallest granules or elements. They are connected and bound by electrical and nuclear forces. Historical stages demonstrated that current provisions of atomic theory had been accumulated with numerous details of atom structure and functionality. Each century brought vital advantages for atomic theory that became represented in all relatively close social sciences.

400 B.C.

Attempts of scientists of Ancient Greece to explain the nature of atom gave a rise to atomic theory. Atom appeared in the studies of Democritus, Greek philosopher approximately in 400 B.C. He interpreted atoms as the elements of any substance or matter, whether it seemed steady and smooth (Grammaticos & Diamantis, 2008). In fact, these atoms are invisible and separately imperceptible. Simple explanation of Democritus’ opinions led to ability of any substance to be divided on the smallest undivided elements that were called atoms. Connections between them explain the emergence of changes of the world and universe. In opposite, atoms remain undivided and stable.

350 B.C.

Relatively close engagement in atomic theoretical provisions characterizes the contribution of Aristotle who had defined atom as an element. This Greek philosopher argued that elements composed any surrounded environment that could be decomposed into the smallest indecomposable parts. These parts were called elements. The ability of a substance to be divided became the practical complexity and the challenge for many researchers of those times. The interweaving of physical and philosophical aspects characterized historical stage of atomic theory. Following Democritus, Aristotle provided scientific methods of data gathering and collecting that constituted the basic processes of scientific study. Although ancient Greeks’ assumptions were filled with philosophical provisions, they brought a name to atom.

  • 1704

Atomism dominantly prevailed in scientific views during a long time before the nineteenth century. Nevertheless, year 1704 was distinguished by the progressive studies of the French researchers Lavoisier and Newton. Lavoisier provided the formulation of conservation during chemical reactions and distinguished compound and element, while Newton advanced the persuasion regarding mechanical universe with solid elements in motion. Their contributions lied in the basis of early background of atomic theory.

  • 1803

A British scientist John Dalton proposed the provisions of atomic theory that were concerned with solid masses of atoms and their measurable properties. According to Dalton, elements have different composition made of the identical atoms (Viana & Porto, 2010). They have a mass and motion. The scientist investigated the conduct of gases during chemical reactions and made the assumption that every chemical element possesses inherent and unique atom. Different combination and mixture of atoms in various proportions form distinguishing chemical substances of nature. Dalton proposed Billiard Ball Model to determinate the structure and form of atom.

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This model was named because of the spherical form of investigated atoms of gas that were closely located to each other. Dalton’s investigations were reflected in the depiction of this atom model.

  • 1811

Theoretical and practical contributions of Amedeo Avogadro to atomic theory were connected with experimental investigation of gas’ atoms and their molecular weights (Hanwell et al., 2012). In his studies, this Italian chemist discovered the peculiarities and composition of gases. The results significantly simplified the current practice of chemistry improvement. Due to specifics of French chemistry of his days, these progressive findings were somewhat neglected. Later, he was acknowledged for facilitating and overcoming the complexities of previous generations with simple transformation of the oxygen molecules.

  • 1832

Although Michael Faraday was not the atomism follower, he was the researcher of electricity’s actions and the founder of electrolysis. The scientist developed the provisions of electrochemistry. His advancements in promotion of atomic theory were in the discovery of electrical component of atom. Due to practical experiments with electrodes and water, he proved the functional roles of electrical forces that compound atoms together (“Modern Atomic Theory”, 2007).

  • 1859

One of the completed tube of cathode-ray was built by Julius Plucker, a German chemist, physicist, and mathematician. He carried out the experiment that demonstrated gas discharge and electron rays. His researches motivated further development of the provisions of atomic theory.

  • 1869

This stage of atomic theory was remarkable owing to the findings of Dmitri Mendeleev, the originator of the periodic table. He grouped chemical elements with similar properties into certain groups and assumed that these properties could be periodically changed according to the changes of atomic mass. This assumption constituted the basis of the Periodic Law (Scerri, 2007).

  • 1870

Few decades later, William Crookes, a scientist from England, found that cathode rays moved in straight lines with heat production (Fournier d'Albe, 1923). He developed appropriate tube for cathode ray that became a contribution for promotion of television. Thus, researches of atom as a scientific object initiated particular advancements in other social areas of human life.

  • 1896-1898

Atomic theory was supplemented with the German advancements of Wilhelm Conrad Roentgen who discovered x-rays during experimental investigation of Crookes’s tube of cathode-ray. Roentgen revealed that chemicals become glowering during interaction with the rays of cathode. These rays withstand magnetic field. In addition, this year was notable for the researches of certain radioactive matters by the French investigator Henri Becquerel.


Year 1898 was remarkable because of the discovery of electron and development of plum-pudding model of an atom composition. These advancements were made due to the efforts of J.J. Thompson from the scientific community of England. This scientist made the contribution to the atomic theory through the experiments with the tube of cathode ray and improved the atomic model with the characteristics of positively or negatively charged elements.

Design of this model was conditioned by the determined positions of electrons around the center, their motion, and distribution within an atom, like plums inside a pudding. The radius of their movement was also estimated due to Thompson’s practical approach (Greenberger, Hentschel, & Weinert, 2009).

  • 1900

German scientist Max Planck laid the origins of the provisions of the quantum theory. He declared that electromagnetic energy could shape quantizing form during emission (Ade et al., 2014). His attempts were dedicated to investigation and assessment of the hot glowering of a matter. Physicists called his quanta as protons.

  • 1908

Robert Millikan discovered such functional peculiarity of the electron as electric charge. Its measure originated fundamental constants of physics. He proved that this characteristic of electron was constant in the design of atomic model and it demonstrated atom dynamics. Millikan also considered that electricity had its atomic structure. Moreover, he applied Einstein’s equation in experimental conditions and made photoelectric determination of the constant by Planck (The Nobel Foundation, 2015). These contributions were notable for current understanding and exploration of physical phenomena.

  • 1909

Experimental findings of Ernst Rutherford were successful owing to his rationale about the central location of atom’s mass, its ball form, and positive charge. It was significantly important for further consideration and improvement of atomic theory and its practical exploration. The scientist demonstrated functionality of atomic nucleus. His version of the planetary model of atom is illustrated as the travelling of electrons around the center of atom just like the motion of planets that orbit the Sun.

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Atomic model was improved by Neils Bohr (Kragh, 2012). He supplemented it with the motion of electrons that travelled across orbits and determined the number of the electrons that functioned in exterior orbits.

Planetary model of atom developed by Bohr illustrates the motion of atom’s elements governed by energy’s quantum and the mechanism of lights emission due to transition of electrons in orbits and stable position of inner proton. In addition, Bohr used the Planck theory of quantum in explanation of the phenomena and stated that the emission of energy’s quantum by electrons changed their position in orbits.

  • 1914

Along with comprehensive improvement of atomic model and development of peculiarities of chemical elements, investigation of atom was continued with the participation of Henry Moseley. This British physicist determined atomic number of a chemical element by the number of its internal protons. His researches were also concerned with nuclei’s charges in atoms.

  • 1923

Atomic researches were continued by Louis de Broglie who discovered duality in protons’ nature towards waves and particles. In his researches, de Broglie supported the physician provisions of Einstein.

  • 1926

The Austrian physicist Erwin Schr?dinger made his contribution due to wave equation connected with the motion of small elements governed by waves that, in turn, became altered under the influence of external provocative (Nakashima, Hijikata, & Nakatsuji, 2008). From the position of math, Schr?dinger described the direction of electrons’ movement in form of a wave and changes of a quantum system with time passing. He developed Quantum mechanical model of atom.


This model was based on Bohr atomic model and it illustrated probability of electron position during the motion around the atomic nuclei. The picture gives an idea of electron cloud formed around atomic nucleus.

  • 1927

The founder of quantum mechanics Werner Heisenberg developed the description of atom with the usage of frequency of spectral lines. Along with this contribution, the scientist offered indeterminacy principle proclaimed the complexity of simultaneous verification of a particle’s velocity and location. This rule enabled current researches to be logically and thoughtfully structured.

  • 1935

James Chadwick was awarded with the Nobel Prize for the discovery of the neutron, as the electrically neutral elements with the similar weight as of the protons (Chadwick, 2012). This discovery supplemented current understanding of atomic structure. His investigation was based on the behavior of the protons of polonium.

  • 1964

Among the latest researches of atom structure and characteristics, there were findings of Murray Gell-Mann and George Zweig, the U.S. scientists, who brought the presentation of particular quarks as the particles of a matter serving for explanation of complicated chemical substances. Development of atomic theory was supplemented by examination of these non-subtractive elementary particles.


Thus, long history of formation of atomic theory brought numerous detailed studies dedicated to atom, structure, and functionality. Starting from complicated philosophical background, theoretical provisions of atom examination continued with current researches of its complicated physician and chemical peculiarities. Significant contributions of numerous scientists all over the world were remarkable for the present advancements of atomic theory. Atom researches led to the scientific discoveries and improvements. Particular scientific disciplines were combined and collaborated during the history of atomic theory formation. Such connections favored better and thoughtful consideration of atom and its abilities to be applied in important areas of social life.

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