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Democritus 400BC
Democritus was born in 460 BC, in Greece. He was the first to claim that all matter is made up of atoms; atoms cannot be physically separated from each other, there is, empty pace between each atom, they are indestructible, they are always in motion and that there is an infinite number of atoms and kinds of them which can be all shapes and sizes. He stated, “The more any indivisible exceeds, the heavier it is.” -
Antoine Lavoisier
Antoine Lavoisier was the one who proved the law of conservation of mass. He did in approximately the year 1789. The law of conservation of mass sais that mass be created or destroyed and that the mass of products must equal the mass of reactants. Also Antoine Lavoisier proved that when oxygen and hydrogen combine, water is formed from them. -
Joseph Proust
Joseph Proust published his Law of Definite Proportions or Law of Constant Composition, in 1794. The Law of Definite Proportions states; a compound is made up of exact proportions of elements by mass, regardless of which way the compound was created. For example to make water, there has to be a specific ratio of grams of hydrogen to oxygen regardless of where the water is from. -
John Dalton
John Dalton based his theory on the principle that atoms of different can be distinguished by the differences in their weight. His theory proposed that: • All matter is composed of atoms.• Atoms can’t be created or destroyed.• Atoms of the same elements are all identical.• Different elements have different types of atoms.• When atoms are rearranged, chemical reactions occur.• Compounds are formed from atoms of essential or basic elements. -
Wilhelm Roentgen
Wilhelm Roentgen lived from 1845 to 1923 and he was a German physicist. He accidentally discovered x rays in 1895 and this dramatically changed the fields of medicine and physics. This also helped to prove the existence of electrons in atoms. An x-ray is a type of radiation, which can penetrate materials that light isn't able to. For this, Wilhelm Roentgen received the first ever Nobel Prize -
JJ Thompson
In the year 1897, JJ Thompson discovered the electron. His work was the birth of the theory that atoms are made up of small particles. His theory was proved using a cathode ray tube. Doing this he discovered that there were smaller particles than an atom, electrons. It was then proved that atoms were made up of protons, electrons and neutrons. -
Max Planck
Max Plank Was a German Physicist, born on the 23rd of April 1858 and died on the 4th of October 1947. He suggested the quantum of action, which is now known as Planck’s constant h. It explained the intensity of a pattern of light, which emitted at any frequency off a black body. In simpler terms, energy isn't a continuously flowing unit, but it is carried in smaller irregular units. He called these ‘quanta’. His theory was called, ‘The Law of Energy Distribution in the Continuous Spectrum. -
Ernest Rutherford
Ernest Rutherford was born on the 30th of August 1871 and he died on the 19th of October 1937. In 1907 Ernest Rutherford, Hans Geiger and Ernest Marsden attempted to examine the structure of an atom using the Geiger-Marsden experiment. The results demonstrated the existence of the atomic nucleus and it then was an important part of the Rutherford model of the atom. The Rutherford model of the atom is the one where it shows electrons circling the nucleus. The element ‘rutherfordium’, was named a -
Robert Millikan
JJ Thompson’s hypothesis of the mass of an electron was that a singles electron was at least 1000 times less than the smallest atom.So in 1908, Robert Millikan measured the charge on an electron using an oil drop apparatus. Oil droplets were sprayed onto a sample chamber and some droplets would fall through a pinhole into an area between a positively charged plate and a negatively charged plate, which was ionized by x-rays. Particles that didn’t capture electrons fell to the bottom and the ones -
Antonius Johannes Van Den Broek
Antonius Johannes Van Den Broek was born on the 4th of May 1870, and died on the 25th of October 1926. He was a Dutch amateur physicist who was the first person to realize in 1913, that the number of an element on the periodic table matches the charge of its atomic nucleus. -
Henry Moseley
Henry Moseley was a British chemist who lived from 1887 to 1915. He studied with Ernest Rutherford and developed the submission of x-ray fields to study the atomic structure. As a result of Moseley’s discoveries, aperiodic table with more accurately positioned elements was produced by closer determination of atomic numbers. In 1913, Henry Moseley measured the wavelengths of the x-ray spectral lines in some elements. This showed that the ordering of the wavelengths of the x-ray secretions of the -
Niels Bohr
Niels Bohr was a Danish physicist who was born in 1885 and died in 1962. Niels Bohr’s main goal was to research the structure of the atom and in 1913; his theory of the atomic structure was complete. His theory was a mixture of both Ernest Rutherford’s work and Planck’s Quantum Theory. Bohr declared that an electron could orbit the nucleus, but it could only do this in discrete orbits, which didn’t release any radiation. -
Louis De Broglie
Louis De Broglie was a French quantum physicist who was born on the 15th of August 1892 and died on the 19th of March 1987. In 1924 he had a theory of wave duality. He had seen that instead of light matter being against one another, waves or ‘radiation’ can behave like particles and particles can behave like waves. His theory helped to explain the theory of wave functions, by Erwin Schrodinger. -
Erwin Schrodinger
Erwin was an Austrian physicist, born on the 12th of August 1887 and he died on the 4th of January 1961. He developed a powerful atomic model in 1926. For the distribution of electrons in an atom, he combined the de Broglie equation to generate a mathematical model. The model contains wave functions (mathematical equations) to fulfil the needs placed on the behaviour of electrons. The disadvantage of this model is that it is hard to think of a physical model of electrons as waves. -
James Chadwick
James Chadwick was born on October 20th 1891 and he died on July 24th 1974. James Chadwick discovered the neutron by using some work of Irene Joliot Curie. She found out that a beam of high penetrating power was created, when beryllium was combined with positively charged alpha particles. From here, James knew that it wasn’t caused by either electric or magnetic fields, and he figured that it was contained neutral particles, neutrons.
