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Democritus (BC)
Democritus was born in 400BC and doed 370 BC. He lived in Greece. He is so important because he started the whole idea that led to modern theory. Democritus never did any experiments to prove his theroy it was based on thoughts and reasoning. He’s atomic model relied on similarities of the human senses. Democritus thought that matter is made up of small unbreakable units which he called atoms. Democritus was the very first to suggest any type of atomic theory. -
Jan 1, 624
Thales (BC)
Thales was born in 624 BC and died in 546 BC. He lived in Greece. Thales suggested the idea that water was the start of all matter. This isn’t entirely true but helped develop of the atomic model. Water is essential for living, and the first life forms came from the oceans. Because of these reasons scientists were bale to use he’s theory and enhance it to create their own theory. Thales's theory wasn’t proven wrong until the 1700’s. -
Isaac Newton
He was born on the 25th of December 1642 and lived in Lincolnshire England. He died 20th March 1727 in Kensington, England. Isaac Newton is known for inventing Calculus and the reflecting telescope. He also went against scientific principles like the three laws of motion and the laws of gravity. He was able to show that all objects in our universe attract each other by gravitational force. -
Antonie Lavoisier
He was born August 26th 1743 and died May 8th 1794. He lived in France. He studied the composition of chemical compounds. He discovered that compounds containing more than one element would no matter what have the same amount of each element. By learning this he came up with the Law of Conservation. This means matter can't be made or destroyed. An experiment used to come up with his law was turning mercury and oxygen into mercury oxide. He started the conservation on what exactly an atom was. -
Robert Brown
Robert Brown was born December 21st 1773. He lived in Scotland and England. He died June 10th 1858. He is known for creating the Brownian motion. He put pollen grains on water and found that the grains constantly changed paths like they were bumping into something invisible. Robert Brown discovered that the Pollen grains were bumping into particles of water. -
Joseph John Thomson
Joseph John Thomson was born on December 18th 1856. He died August 30th 1940 and lived in England. Joseph is most known for discovery that atoms actually were actually capable of being divided and made up of even smaller negatively charged particles. We know this as electrons. His discovery led him to suggest that an atom is like a plum pudding. What he meant by this was that the positively charged material was the cake and the electrons were the fruit. -
Hantaro Nagaoka
Hantaro Nagaoka was born on August 15th 1865. He died December 11th 1950. He lived in Japan. Hantaro Nagaoka worked on spectroscopy. He made a model of an atom using similarities to Saturn’s rings early on but was wrong. He came up a theory that the nucleus was really big and that the electrons surrounding the nucleus were held by electrostatic forces. So he saw this as the nucleus being a planet the electrons being the rings orbiting Saturn bounded by gravity. -
Robert Andrews Millikan
Robert Andrews Millikan was born on March 22nd 1868. He died December 19th 1953 and lived in the United States. Robert measured the charge of an electron by using an oil drop and worked on the photoelectric effect. This was able to help other scientist to understand the atom and proved Joseph John Thomson’s hypothesis wasn’t exactly true. -
Ernest Rutherford
Ernest Rutherford was born August 30th 1871 and died October 19th 1937. He lived in Britain but was born in New Zealand. He is most recognized for doing the gold foil experiment. This experiment was able to get him to understand the inside of an atom. Ernest found out that the nucleus is in the middle of an atom. He also found out that an atom is mainly empty with a large amount of positive charges. A new model of an atom was then made. This was called ‘The Rutherford nuclear model’. -
Niels Bohr
Niels Bohr was born October 7th 1885 and died November 18th 1962. He lived in Denmark. Niels Bohr learned and studied the atoms structure. He said that electrons in the atom orbit around it. He also said the more energy the electrons have the further they orbit from the nucleus. He suggested outer orbit of an atom could hold more electrons than the inner orbit. Because of Niels Bohr and the ‘Bohr model of the atom’ scientists were given more knowledge as to why atoms bond. -
Henry Moseley
Henry Moseley was born on November 23rd 1887 and died August 10th 1915. He lived in England. Henry Moseley created the application of “x-ray spectra” to learn the design of an atom. He found out that the number of protons in an element depends on its atomic number. He found this out by measuring the wavelength of the x-rays given off by certain metals and from that he could find the number of protons in the nucleus of an atom. This was the beginning of the atomic number. -
James Chadwick
James Chadwick was born October 20th 1891 and died July 24th 1974. He lived in England. James Chadwick is responsible for discovering neutrons. He was able to realize that they were different as they repelled electrical forces that are found in the nucleus of lots of atoms. James Chadwick was able to prove that neutrons, which make up half the mass of an atom, existed. -
George Johnstone Stoney
George Johnstone Stoney was born 15th February 1826. He died on the 5th July 1911. He lived in Ireland and England. George is most known for his theory that electricity was made up of separate negatively charged particles. He called these electrons. When introducing electrons he said they were "fundamental unit quantity of electricity". -
John Dalton
John Dalton was born on the 6th September 1766 and died 27 July 1844. He lived in England. John Dalton is most known to be the first person to describe colour blindness as well discovering the Dalton’s Law which explains the relationship of Partial Pressure. He was influenced my Democritus idea of the small unbreakable matter called “Atoma”. -
Aristotle (BC)
Aristotle was born in 384 BC and he died in 322 BC. Aristotle lived in Greece. He didn’t think that atoms exist or that they could be in constant motion. He came up with a theory based on the four elements: fire, water, earth and air. Aristotle believed that to understand something you just had to think about it. No one agreed with his theories until the 17th century. He slowed the atomic theory down by saying they didn’t exist.
