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Democritus
Democritus was a Greek philosoper. He is seen to be the father of modern science. He based his theorys on hypotheses rather than experiments. He believed that everything was made up of atoms. That they are indestructible, that there are infinite amounts of atoms & types of them. He believed they came in different shapes and sizes & that there is empty spaces between them all. Being the first to suggest a type of atom, he was the most important to what the atomic theory is in modern science. -
Jan 1, 624
Thales
Thales of Miletus was a Greek philosopher. He lived from 624BC–546BC. He believed and suggested that water was the basis and origin of matter. His proposal did prove to be partly true, which contributed to us knowing more about the atom. Water is necessary to life and the first life forms were formed in water (the oceans). Thales theory about water contributed to a lot of other scientists forming their own atomic theories. Same as Aristotle his beliefs were also used for around 2000 years. -
Sir Isaac Newton
Isaac Newton was born 4th January 1643 & died 31st March 1727. He was an English physicist and mathematician. Known to be one of the most influential people of all time. He studied gases & the existence of atoms. He believed their were minuscular pieces of mass “swimming” everywhere. He also believed a mechanical universe where small solid masses were constantly in motion. Suggesting that atoms were all held together by force & also believed that mass was made of solid, indestructable particles. -
Antoine Lavoisier
Antoine Lavoisier was Born 26 august 1743 in Paris, France and died 8 May 1794 also in Paris. He is said to be “the father of modern chemistry”. He was the first to discuss what an atom was exactly. Coming from his chemistry experiments he came up with the Law of Conversion of Mass, this meant that matter could not be created or destroyed. One of the most famous experiments and the main one he did to come op with the law was turning mercury (Hg) and oxygen (O) into mercury oxide (HgO). -
John Dalton
John Dalton was born September 6th 1766 & died July 27th 1844. An English chemist & meteorologist who is remembered most for his contribution to the modern atomic theory. He made multiple discoveries such as:
-all matter is made up of atoms
-atoms cannot not be destroyed nor made
-atoms of the same element are the exact same
-different elements contain different atom types.
-when atoms are rearranged it causes a chemical reaction
His theories contributed hugely to what the atomic theory is today -
Robert Brown
Robert Brown was born on 21st December 1773 in Montrose, Scotland & died on June 10th 1858. He studied medicine at University of Edinburgh. He did an experiment where pollen grains were put on water, observations showed that the grains changed directions continuously in random patterns. From this he discovered that it was water paticles causing the pollen to change directions randomly. This movement has been named the Brownian motion, after Robert Brown. -
George Johnstone Stoney
George was born on the 15th February 1826 in Ireland and died 5th July 1911. He was a physicist. He is remembered for his theory that electricity was made of separate, negatively charged, particles he called electrons. Initially introducing electrons as the "fundamental unit quantity of electricity". His findings of the “electron” further contributed significantly to the eventual discovery of the particle in 1897 by Joseph John Johnson. -
Joseph John Thompson
Sir Joseph John Thompson, also known as J.J. Thompson was born in Manchester, England on 18th December 1856 & died on 30th August 1940. He was a physicist. He made a changing discovery that atoms were made up of smaller negatively charged particles, now known as electrons. He came up with the J.J. Tjompson plum pudding model. He compared the atom to a plum pudding, The cake was the positively charged metals & the fruit inside was the electrons. He was also the first to say the atom was a sphere. -
Hantaro Nagoka
Hantaro Nagoka lived from the 15th August 1865 to the 11th December 1950 in Japan. He rejected all the claims made by Thomson & believed the atom was similar to Saturn and its rings. He believed the nucleus was massive & that like the rings revolving around Saturn, that the electrons revolved around the nucleus du to the electrostatic forces. A lot of this was confirmed, however many parts were incorrect. This still set the base for the Bohr Model made by Ernest Rutherford & Niels Bohr in 1913 -
Robert Andrews Millikan
Robert A. Millikan was born on March 22 1868 and died on the 19 December 1953. He was an American experimental physicist, he was extremely passionate about being hands on in physics. Millikan made a big discovery and is most known for measuring the charge of an electron with an oil drop. -
Ernest Rutherford
Ernest Rutherford was born on 30th August 1871 in New Zealand and died on 19th October 1937 in England. He studied physics and chemistry. He is most known for “the Gold Foil experiment". His worked helped to better understand the inside of an atom. He found that there was a nucleus directly in the center of the atom, but also that the atom is mostly made up of empty space with big amounts of positive charges (neutrons). This is known as the Rutherford Nucleur Model. -
Henry Gwyn Jeffreys Moseley
Henry Moseley lived in England from 23rd November 1887 to 10th August 1915. Moseley used the method of X-ray spectroscopy to study the structure of the atom. By measuring the wavelength of the x-rays given off by specific metals, he could find how many positive charges (protons) there were in the nucleus of an atom. All of this then determined that however many protons in an element, determines the atomic number. This was the first concept of the atomic number. -
Aristotle
Aristotle was born in 384 BC in Chalcidice, Greece. He attended Plato’s Academy in Athens, where he remained for nearly 20 years. He was the first man to study the Atom. He didn't believe that atoms could exist or that they could always be moving. He believed all matter was made up of four elements: air, earth, water, fire and that to these elements their were 4 qualities: wtness, dryness, coldness and hotness. Although this theory was used for 2000 years it was further proven as false.
