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He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air.
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He theorized that all material bodies are made up of indivisibly small “atoms.”
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Earliest Greek to develop the theory of atomism
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Discovered Boyle's law expresses the inverse relationship that exists between the pressure and volume of a gas
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Lavoisier found that mass is conserved in a chemical reaction. The total mass of the products of a chemical reaction is always the same as the total mass of the starting materials consumed in the reaction.
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Lavoisier reported that water was roughly 85% oxygen and 15% hydrogen by weight. Water therefore seemed to contain 5.6 times more oxygen by weight than hydrogen.
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Discovered of the law of definite proportions in 1793
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1.) The first part of his theory states that all matter is made of atoms, which are indivisible and indestructible
2.) The second part of the theory says all atoms of a given element are identical in mass and properties.
3.) The third part says compounds are combinations of two or more different types of atoms.
4.) The fourth part of the theory states that a chemical reaction is a rearrangement of atoms. -
Discovered the law of multiple proportions, also known as Dalton's law,
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1st fact - In 1811 he claimed that equal volumes of all gases at the same temperature and pressure contain the same number of molecules. This is now called Avogadro’s law.
2nd fact - His experiments in 1811 helped inspire Avogadro's constant which he did not create -
Made one of the most significant discoveries that led to the idea that atoms had an electrical component. Faraday placed two opposite electrodes in a solution of water containing a dissolved compound.
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1st fact - In 1869 he created the first Periodic Table.
2nd fact - In 1869 he discovered periodic law also called Mendeleev's law -
He had introduced the concept of the electron, though not the word, as early as 1874, initially naming it "electrine"
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Discovered positive particles or rays in 1886
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Introduced the term electron as the "fundamental unit quantity of electricity" in 1891
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In 1895 he settled the cathode ray particle-wave debate by demonstrating that cathode rays carry negative charges and are thus particles.
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Discovered the radioactivity in uranium in 1896
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Marie came up with a new term called “radioactive.” in 1896
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J.J. Thomson's experiments with cathode ray tubes showed that all atoms contain tiny negatively charged subatomic particles or electrons.
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1st fact - In 1898 along with Marie discovered polonium
2nd fact - In 1898 along with Marie discovered radium -
1st fact - In 1898, Marie discovered a new element that was 400 times more radioactive than any other. They named it “polonium,”
2nd fact - In 1898 announced the existence of another element they called “radium,” It gave off 900 times more radiation than polonium. -
Discovered the quantum of action, now known as Planck's constant, h, in 1900
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Thomson proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."
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1905 Hahn discovered a new substance he called radiothorium (thorium-228), which at that time was believed to be a new radioactive element.
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In 1908, Geiger introduced the first successful detector of individual alpha particles.
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Millikan began a series of experiments to determine the electric charge carried by a single electron. The results suggested that the charge on the droplets is a multiple of the elementary electric charge
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In 1909 Rutherford disproved Sir J.J. Thomson's model of the atom as a uniformly distributed substance.
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In 1909, Hahn discovered radioactive recoil.
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1st fact - made the Rutherford model which is a description of the structure of atoms proposed in 1911
2nd fact - discovered protons in 1911
3rd fact - discovered the nucleus in 1911 -
1st fact - In 1913, Niels Bohr proposed a theory for the hydrogen atom based on quantum theory that energy is transferred only in certain well defined quantities.
2nd fact - 1913 made the Bohr Atomic Model which looks like a solar system -
1st fact - In 1913 he used self-built equipment to prove that every element's identity is uniquely determined by the number of protons it has.
2nd fact - In 1913 he predicted confidently the existence of four new chemical elements, all of which were found. -
Conclude in 1913 that certain elements might exist in forms that differ in atomic weight while being indistinguishable and inseparable chemically. Called isotopes
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In 1924 Louis de Broglie introduced the idea that particles could be described not only as particles but also as waves.
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1st fact - In 1926 Erwin Schrödinger formulated a wave equation that accurately calculated the energy levels of electrons in atoms.
2nd fact - 1926 Erwin Schrödinger proposed the electron cloud model of the atom -
In 1932 Chadwick discovered neutrons
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He inadvertently discovered nuclear fission during an experiment in which the uranium atom split into barium
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In 1938, Lise Meitner discovered that nuclear fission can produce enormous amounts of energy
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In 1939 coined the term nuclear fission
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