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500
Democritus (BC)
Democritus was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He thought hard about matter and the universe and thought of an atomic theory. In 5th century BCE, Democritus stated that all matter was made up of tiny units that moved around. He believed that these units are invisible and unchangeable. He decided to call these tiny units atomos, which in Greek, means uncuttble. -
Jan 1, 600
Kanada (BC)
During the 6th centuary BCE, a man named kanada, who founded the aishesika school of philosophical came up on his own atomic theory. His idea was that matter was made on a finite number of paramaṇus (atoms) which were indivisible and eternal. Atoms make up the 4 elements water, fire, earth and air, which make up matter. They believed that the interactions between these atoms, causing them to combine was caused by the will of shvara, a Hindu god -
Antoine Lavoisier
Antoine Lavoisier was born on 26th of august 1743. Lavoisier named oxygen in 1778, hydrogen in 1783 and predicted silicon in 1787. He put together the very first list of all elements, helped construct the metric system and helped reform chemical nomenclature. In 1777 he was the first person to establish that sulphur was an element, instead of a compound. He was also the one who discovered that the mass of the matter always remains the same, although the matter may change in shape or form. -
Joseph Proust
Joseph Proust was born on September 26, 1754 and died on July 5 1826. Proust studied different sources of compounds and discovered that they contained some ratio by the weight of their element. His conclusion was that a given compound always has the same elements In the same proportion by mass. -
John Dalton
John Dalton was born on September 6, 1766 and died July 27 1844. Dalton discovered that atoms are the small particles that make up an element, and that atoms cannot be subdivided, created or destroyed. He also made another discovery that during a chemical reaction, atoms are combined, rearranged or separated. -
Amedeo Avogadro
Lorenzo Romano Amedeo Carlo Avogadro is most famous for his contributions to the molecular theory. he suggested that "equal volumes of all gases at the same temperature and pressure contain the same number of molicles" known as avogadro's principle (or law) -
Dmitri Mendeleev
Dmitri Mendeleev was born at Tobolsk, Siberia in 1834 and died in 1907. Mendeleev created the very first version of the periodic table of elements. He arranged all elements into 7 groups with smaller properties. He used the periodic table of elements that he created to predict the properties of elements that were yet to be discovered. Element 101 MD (Mendelevium) was named after him. -
George Johnstone Stoney
George Johnstone Stoney was born 15th of February 1826. He was an Anglo-Irish physicist. In 1891, he proposed the term 'electron' to describe the ‘fundamental unit quantity of electricity’. What stoney contributed to the atomic theory, led to the discovery of the particle by j.j Thomson in 1897. -
J.J Thompson
Sir Joseph John "J. J." Thomson was born in Manchester, Lancashire, UK on 18 December 1856 .JJ Thompson discovered electrons and isotopes, and invented the mass spectrometer. in In 1904, he came up with the idea of comparing electrons to a plum pudding. This is known as the plum pudding model. If you imagine the pudding itself being positively charged, and the plums, scattered through out the pudding are the negatively charged electrons. -
Marie Curie
Marie curie was a polish physic and chemist best known for her contribution to the atomic theory, by her research on radioactivity. She also discovered 2 elements, radium and polonium. -
Ernest Rutherford
Ernest Rutherford discovered that the atomic nucleus was dense, small and positively charged he Studied radiations made from uranium and thorium and named them alpha and beta Rutherford took a piece of gold foil. He shot alpha particles at it. Some of the particles were knocked back, discovering that it was the nucleus which was deflecting these particles. This was known as the gold foil experiment -
Hans Geiger
German physicist, Hans Geiger is most famous for being the co-inventor of the ‘geiger counter’ and the ‘geiger-marsden experiment’ in which discovered the atomic nucleus. He also discovered the Geiger-Nuttall law and performed experiments in this area, which laid the foundations for Rutherford's atomic model -
Niels Bohr
Niels Henrik David Bohr was a Danish physicist, born October 7 1885. He made functional contributions to understand the atomic structure. It was bohr who is responsible for creating the ‘bohr model of the atom’. The concept of the model was for the electrons to orbit around the centred atomic nucleus, which was compared to the planets orbiting around the sun -
Louis de brogile
In 1924 Louis de brogile discovered that electrons could behave as waves in some conditions. This helped scientists understand that atoms do not behave like the solar system, because unlike the solar system, electrons do not move in regular orbits. This theory and discovery supported Einstein. -
enrico Fermi
Enrico Fermi was an Italian-American physicist most noted for his work on the development of the first nuclear reactor. It was made by energy from the atom nucleus being released.
