• 460 BCE

# Democritus

Democritus was the first to say that the matter was composed of atoms, Democritus showed interest in the first principles
Democritus assumed that all matter was composed of solid particles invisible to the eye of the human, because this is considered the first to discover the atom.
Democritus discovered the atom in a theoretical way(anónimo,s.f.) Retrieved from:anónimo, s.f. areaciencias, http://www.areaciencias.com/DESCUBRIMIENTOS%20CIENTIFICOS/Descubrimiento-del-atomo.htm
• 460 BCE

# Democritus.

It is believed that Democrito traveled by Diatintos places like Egypt, Persia and Mesopotamia acquiring knowledge of theology, astrology, geometry, in addition to this Democrito wrote about the ethics proposing that happiness was the greatest good (Moreno. V, s.f.). Retrieved from: Moreno. V, s.f., buscabiografias, https://www.buscabiografias.com/biografia/verDetalle/595/Democrito
• 450 BCE

# Democritus

he knew that if you take a stone and cut it in half, each half has the same properties as the original stone and that if you continued to cut the stone into smaller and smaller pieces, reach a point so small that it could no longer be divided . He called these infinitesimally small fragments of matter "indivisible" atoms(Casanova.F, 2017) Retrieved from:Casanova.F, 2017,hdnh, https://hdnh.es/la-teoria-del-atomo-de-democrito/
• # John Dalton

Eaglesfield,Great Britain1776-Manchester1844
John dalton was a chemist and physicist who was given the first formulation of the atomic theory, his insatiable curiosity and desire for curiosities allowed him to compose his academic training and to have recognition for his scientific work
John Dalton's work was based on gas and a visual illness that he suffered from, color blindness(Copérnico.N,2004) Retrieved from:Copérnico.N,2004,biografiasyvidas, https://www.biografiasyvidas.com/reproducir.htm
• Period: to

## John Dalton

When he was already recognized as a scientist, Dalton discovered the law of multiple proportions that was based on the weight of the elements that intervene in a chemical reaction.From this he proposed the complete theory on the constitution of matter that took up the Greek atomism (anonimo, 2004). Retrieved from: Copérnico.N, 2004, biografiasyvidas, https://www.biografiasyvidas.com/reproducir.htm
• # John Dalton

In 1793 he published his first book (meteorological observations and essays) defending the thesis of the merely physical air of gases.(anonimo, 2004). Retrieved from: anonimo, 2004, biografiasyvidas, https://www.biografiasyvidas.com/reproducir.htm
• # Dalton

At the age of 26, he supposed that he and his brother did not distill the colors, in a scientific article (extraordinary facts related to the vision of colors in 1974 that later is known as color blindness)(anonimo, 2004). Retrieved from: anonimo, 2004, biografiasyvidas, https://www.biografiasyvidas.com/reproducir.htm
• Period: to

## John Dalton

Dalton used his theory to explain the existence of the atom, Dalton's error was to say that the atom was indivisible, which is false today, was missing by discovering the neutron, the proton, the electron and the nucleus of the atom (anonimo, 2004). Retrieved from: anonimo, 2004, biografiasyvidas, https://www.biografiasyvidas.com/reproducir.htm
• # John Dalton

The Greek atomism is the so-called atomic model of dalton, the first model with scientific bases and was, was proposed in 1803, it said that all the elements that existed are constituted by atoms and these were the smallest that were between the matter (anonimo, 2004). Retrieved from: anonimo, 2004, biografiasyvidas, https://www.biografiasyvidas.com/reproducir.htm
• # Joseph John Thomson

Nation: Cheetman Hill, United Kingdom, 1856.
He died: Cambridge-1940
Thomson was a British physicist, he obtained his studies at the University of Manchester and the Trinty College of Cambridge(anonimo, s.f.). Retrieved from: anonimo, s.f. biografiasyvidas https://www.biografiasyvidas.com/biografia/t/thomson.htm
• # Ernest Rutherford

Nelson, new zealand 1871- London 1937
Rutherford was a physicist, British chemist, in 1893 he graduated in Christchurch, New Zealand(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm
• # Thomson

Thomson research investigated the nature of cathode rays and showed that electric fields could cause the deviation of these. it was a result for his friends, an approach to the deviation under the combined effect of electric and magnetic fields(anonimo, s.f.). Retrieved from: anonimo, s.f. biografiasyvidas https://www.biografiasyvidas.com/biografia/t/thomson.htm
• # Niels Henrik David Bohr

1885-1962 Niels died at seventy-seven years, leaving printed some very valuable works as the theory of spectra and atomic constitution.
Bohr was a Danish physicist, due to his contributions and his scientific works he was considered one of the most dazzling figures in contemporary physics(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas,
https://www.biografiasyvidas.com/biografia/b/bohr.htm
• # Erwin Schrödinger

Erwin Schrodinger Vienna-1887, ID 1962.
Schrödinger was an Austrian physicist, in 1906 he entered the University of Vienna, where he remained with brief interruptions until 1920.
He served his country in the First World War and in 1921 he was transferred to Zurich, where he remained for 6 years(anónimo,s.f.). Retrieved from:anónimo, s.f. biografiasyvidas
https://www.biografiasyvidas.com/biografia/s/schrodinger.htm

Manchester 1891- Cambridge 1974
Chadwick was an English physicist and study under the tutelage of ernest rutherford, at the University of Manchester, where he obtained his license in 1911.
He moved to Berlin to expand his knowledge and training under the teaching of Hans Geiger.
his investigations were affected and paused due to the First World War(anónimo,s.f.). Retrieved from:anónimo, s.f. biografiasyvidas https://www.biografiasyvidas.com/biografia/c/chadwick.htm
• # Rutherford

He moved to the University of Cambridge to work as an assistant with John Rutherford(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm
• # Thomson

He discovers a new particle, proving that it was a thousand times lighter than hydrogen, giving it the name of electron, thomson was the first to discover the subatomic particles arriving at important conclusions about these negatively charged particles, with a device that he built He found the relationship between the negative charge and the mass of the electron.(anonimo, s.f.). Retrieved from: anonimo, s.f. biografiasyvidas https://www.biografiasyvidas.com/biografia/t/thomson.htm

• # Rutherford

Rutherford formulated the theory on the natural radioactivity associated with the spontaneous transformations of the elements(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm
• # Thomson

Thomson explained his theory of the atomic structure, he was consisted of a sphere of uniform matter charged positively, where the negative particles were inserted, the same or the electronics, in this model is also known as a puddle of Throws(anónimo, s.f.). Retrieved from: anónimo, s.f., sites.google.com, https://sites.google.com/site/cinthyalizbethhdz18/quimica/modelo-atomico-de
• # Thomson

He performed three experiments with cathode rays, in the 3 Thomson test reached advanced and very important conclusions, called corpuscles to the particles that came from the inside of the interings of the atoms of the electrodes, forming cathodic atoms.The format cathodic rays.With an experiment with the cathode tubes, he concluded that the atoms are divisible(anónimo, s.f.).
• # Thomson

He studied the relationship of the mass between particles that were attracted by the positive pole and by the negative pole of the cathodic tuve (anónimo, s.f.). Retrieved from: anónimo, s.f., sites.google.com, https://sites.google.com/site/cinthyalizbethhdz18/quimica/modelo-atomico-de
• # Thomson

He received the Nobel Prize in physics for his studies on the passage of electricity through the interios of gases(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas,
https://www.biografiasyvidas.com/biografia/t/thomson.htm
• # Rutherford

Start to teaching at the University of Manchester.
He was recognized for his scientific works based on the field of atomic physics, investigated about the arrest of electromagnetic radiation and about the ionization of air produced by x-rays, made a study of radioactive emissions and achieved to classify them in beta, gamma and alpha(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm
• # Rutherford

He showed that alpha particles are helium ions (nuclei of helium atoms)(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm
• # Rutherford

Won the Nobel Prize for chemistry for his work in research and de-integration of elements(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm
• # Rutherford

Discovered new atomic model that would later be perfected by Bohr, in this model there was in the atom a central core in which almost the entire mass was consentrated, as well as the positive electric charges, the shell of the bark of electrons, experimentally demonstrated the theory from the deviations that occurred in trajectory of particles emitted by radioactive substances(anónimo, s.f.)
• # Niels Henrik David Bohr

Bohr completed his higher studies of physics at the University of Copenhagen and obtained a doctor degree.
Having relieved himself as a firm promise in the field of nuclear physics, he went to England to expand his knowledge in the Cavendish laboratory at the University of Cambridge, under the defense of Joseph John Thomson(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas,
https://www.biografiasyvidas.com/biografia/b/bohr.htm
• # Niels Henrik David Bohr

In the study of electrons the doctoral thesis that Bohr had just read in Copenhagen was dedicated, which took to the British territory with the hope of seeing it in, but Thomson was not interested in the work of Niels Bohr, because of this He decided to leave the Cavendish laboratory and go to the University of Manchester(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas,
https://www.biografiasyvidas.com/biografia/b/bohr.htm
• # Niels Bohr

He advantage of the scientific knowledge and teachings of another Nobel Prize winner, Ernest Rutherford and expanded his knowledge about the models of the atom and radioactivity. From then on, between the two scientists established a close contracts by strong ties of friendship(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas,
https://www.biografiasyvidas.com/biografia/b/bohr.htm
• # Niels Bohr

Rutherford developed a theory of the atom that was valid on a speculative level, but could not be sustained in the laws of classical physics, Bohr dared to address the problems that hindered Rutherford's progress with a very simple as well as risky solution:I affirm that the movements that were given inside the atom are governed by some by laws alien to those of traditional physics(anónimo, s.f.) Retrieved from: anónimo, s.f.biografíasyvidas
https://www.biografiasyvidas.com/biografia/b/bohr.htm
• # Joseph John Thomson

Thomson studied the positive rays and the way to use them in the separation of atoms of different mass, achieving the objective by diverting the positive rays in the electric and magnetic fields, with this method I can identify that the neon had two isotopes the neon-20 and the neon-22(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/t/thomson.htm
• # Joseph John Thomson

All the scientific works allowed him to establish a new model of the structure of the atom but the result was incorrect, he assumed that the positively charged particles were mixed homogeneously with the negative ones.
He calculate the amount of electricity transported by each atom and determine the number of molecules per cubic center(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/t/thomson.htm
• # Niels Bohr

The first relevant contributions of Bohr to contemporary physics, said that the internal movements that take place in the atom were governed by particular laws, after this statement Bohr observed that electrons when they are in certain stationary states, stop radiating energy(anónimo, 2015.). Retrieved from: anónimo, 2015. quimicas.net https://www.quimicas.net/2015/05/el-modelo-atomico-de-bohr.html
• # Niels Bohr

Rutherford had spotted a hydrogen atom made up of a proton, and a negative particle that revolved around the proton in the way the planets moved in their orbits around the sun.
Bohr accepted the atomic theory of Rutherford but surpassed it by combining it with quantitative theories, announcement 4 postulates(anónimo, 2015.). Retrieved from: anónimo, 2015. quimicas.net https://www.quimicas.net/2015/05/el-modelo-atomico-de-bohr.html
• # Niels Bohr postulate 1

An atom has a certain number of stationary orbits, in which the electrons do not radiate or absorb energy, even if they are in motion(anónimo, 2015.). Retrieved from: anónimo, 2015. quimicas.net https://www.quimicas.net/2015/05/el-modelo-atomico-de-bohr.html
• # Niels Bohr postulate 2

The electron rotates around its nucleus in such a way that the centrifugal force serves to balance the electrostatic attraction of the opposite charges(anónimo, 2015.). Retrieved from: anónimo, 2015. quimicas.net https://www.quimicas.net/2015/05/el-modelo-atomico-de-bohr.html
• # Niels Bohr postulate 3

The angular momentum of the electron in a steady state is a multiple of h / 2p where h is Planck's quantum constant(anónimo, 2015.). Retrieved from: anónimo, 2015. quimicas.net https://www.quimicas.net/2015/05/el-modelo-atomico-de-bohr.html
• # Niels Bohr postulate 4

when an electron goes from a stationary state of more energy to another of less, the variation of energy is emitted in the form of electromagnetic radiation, the inverse, an electron interacts with a photon which energy allows to pass from a stationary state to another of higher energy
• # Niels Henrik David Bohr

Bohr's atomic model explains the inadequacies of Rutherford's atomic model on the stability of electron orbits.
Bohr postulated that electrons can only be found in certain orbits, because not all orbits were allowed, the distance from the orbit to the nucleus was determined according to the quantum number n (n: 1, n: 2 ...)(anónimo, 2015.). Retrieved from: anónimo, 2015. quimicas.net https://www.quimicas.net/2015/05/el-modelo-atomico-de-bohr.html
• # Rutherford

Achievement the first artificial transmutation of chemical elements through the bombardment of a atom of nitrogen with alpha particles, these transmutations are due to the ability to transform because it has an atom subjected to particles capable of penetrating its nucleus(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas, https://www.biografiasyvidas.com/biografia/r/rutherford.htm

• # Niels Henrik David Bohr

Was awarded as one of the fathers of the atomic bomb with the Nobel prize for physics for his scientific research about the structure of atoms and the radiation that came out of them(anónimo, s.f.). Retrieved from: anónimo, s.f., biografíasyvidas,
https://www.biografiasyvidas.com/biografia/b/bohr.htm
• # Erwin Schrödinger

Schrödinger postulated his atomic model, explaining that electrons are matter waves that are distributed in space according to the function of waves.
The electrons were distributed in orbitals that are regions of space with a high probability of finding an electron, it is determined by the square of the function of orbits(anónimo, 2015) Retrieved from:anónimo, quimicas.net2015 https://www.quimicas.net/2015/05/el-modelo-atomico-de-schrodinger.html?m=1
• # Erwin Schrödinger

The quantum numbers are taken into account (main quantum number n = 1,2,3 .., secondary quantum number or azimuth l= 0,1,2 .., quantum number of external magnetic, (m) values between -1 and +1, spin number (s) direction of electron rotation, values 1/2 y-1/2).The atomic model of schrodinger explains the peropdical properties of the atoms and the bonds that are formed(anónimo, 2015)
• # Schrödinger

Published a series of articles had the basis of modern wave quantum mechanics, which transcribed in partial derivatives differential equation, which would relate the energy associated with a microscopic particle with the wave function described by this particle(anónimo,s.f.). Retrieved from:anónimo, s.f. biografiasyvidas
https://www.biografiasyvidas.com/biografia/s/schrodinger.htm
• # Schrödinger

The schrodinger equation gives as a result wave functions, linked to the probability of a certain physical event, as it can be a specific position of an electron in its orbit around the nucleus(anónimo,s.f.) Retrieved from:anónimo, s.f. biografiasyvidas
https://www.biografiasyvidas.com/biografia/s/schrodinger.htm
• # Erwin Schrödinger

Accepted the invitation of the University of Berlin to occupy the chair of Max Planck and there he met with the most recognized scientists among them Albert Einstein(anónimo,s.f.) Retrieved from: anónimo, s.f. biografiasyvidas
https://www.biografiasyvidas.com/biografia/s/schrodinger.htm

During the investigation and the study of a radiation
detected by walther bothe, chadwick identified the components as particles of a mass equivalent to that of the proton, but loading charges discovering the existence of the neutrons that were components of the atomic nucleus together with the protons that would make the atomic fission possible(anónimo,s.f.) Retrieved from:anónimo, s.f. biografiasyvidas https://www.biografiasyvidas.com/biografia/c/chadwick.htm

He published his scientific papers in the nature magazine, the construction of a cyclotron that rutherford did not see with good eyes was the cause of both leaving friendship and chadwick left for liverpool to start teaching, during World War II(anónimo,s.f.) Retrieved from:anónimo, s.f. biografiasyvidas https://www.biografiasyvidas.com/biografia/c/chadwick.htm

The atomic model of Chadwick was centered in the modeling of the atomic nucleus constituted by protons and by neutrons, in the twenties I can demonstrate the existence of neutral particles, in this time Chadwick made multiple attempts in vain(Torres.J, s.f.). Retrieved from:Torres.J, s.f., lifeder https://www.google.com.co/amp/s/www.lifeder.com/aportaciones-james-chadwick/amp/

Later he replicate the experiments of Irene Curie and Frederic Juliot, this pair achieved the proton proton ejection from a wax sample using gamma rays and supposed that the gamma ray emulation contained neutral particles and these particles were the ones that had hit the wax experiment(Torres.J, s.f.). Retrieved from:Torres.J, s.f. lifeder https://www.google.com.co/amp/s/www.lifeder.com/aportaciones-james-chadwick/amp/

This radiation was impacted with a sample similar to paraffin wax, the protons of this sample were violently expelled from the material, the behavior of the protons was observed by an ionization chamber adapted to the experiment by Chadwick(Torres.J, s.f.). Retrieved from:Torres.J, s.f., lifeder https://www.google.com.co/amp/s/www.lifeder.com/aportaciones-james-chadwick/amp/

It was detected that the behavior of the released protons could be explained if this if the particles had hit other electrically neutral particles t with a very similar mass.