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400 BCE
Democritus
He was born in 460 B.C in Abdera he died 370 B.C. He discovered the universe is made of empty space and tiny bits of stuff, he called those tiny bitts of stuff atoms. He found that atoms couldn't be divided. Because they couldn't be divided they were called atoms because it means uncuttable." He found this by conducting an experiment by breaking a shell until it could no longer get smaller. This gave him the idea that atoms are unbreakable. Democritus was known as the laughing philosopher. -
John Dalton
He started teaching at a school at 12. He was born in 1776 in Egalsfield and died in 1844. He found substances are made of atoms, that atoms of the same element are alike, and atoms of different elements are different. He also saw how atoms can join to make new substances.
Dalton also was able to pull his notes together to propose the first model of the atom, and he described atoms as hard dense spheres that were indestructible. He found these discoveries by experiments with gasses. -
J.J Thomson
Lived from 1856-1940 in Cheetham Hill. Discovered atoms contained negatively charged particles, called electrons. Found that atoms have particles scattered throughout a ball made of a positive charge. The raisin bun model, also known as the plum pudding model. He called it this because the positively charged ball resembled the dough of a bun and the electrons resembled raisins in the dough. Showed all atoms contain electron with cathode-ray tubes. He was awarded a Nobel prize for his discovery. -
Ernest Rutherford
Lived from 1871-1937 in Cambridge. Did many experiments, called the gold foil experiments. He would shoot a beam of particles at a pice of gold foil. Data from these experiments suggested that an atom is mostly empty space with electrons moving around a dense positively charged center. Called the center of the atom the nucleus, he found that the nucleus contained positively charged particles. Called there positively charged particles protons. Was known as the Father of Nuclear physics. -
Niels Bohr
Lived from 1885-1962 in Denmark. Used Rutherford's data to find that electrons move around the nucleus in particular energy levels. The energy levels were determined by the amount of energy the electrons had. The electrons were compared to planets orbiting the sun. This brought him to his conclusion that Electrons closer to the nucleus had less energy, and electrons further from the nucleus had more energy. Used his liquid drop model to find his research, he went to the University of Copenhagen. -
Erwin Schrodinger
Lived from 1887-1961 in Erdberg. Erwin took the Bohr model one step further. Instead of using experiments to discover a new model of the atom he used mathematical equations. His model is known as the quantum mechanical model of the atom. His model didn't define the electrons exact path but predicted th odds of its location. His model shows a nucleus surrounded by an electron cloud where the cloud's probability of finding the electron is greatest. Erwin's cat was dead and alive at the same time. -
James Chadwick
James was the partner of Rutherfurd, Rutherfurd proposed that there must be a second particle in the nucleus but unfortunately never found it. Two decades later Chadwick discovered it then called it the neutron. This was a difficult particle to find because it had no charge. -
Werner Heisenberg
Lived from 1901-1976 in Munich. In 1932 he bombarded beryllium atoms with alpha particles, and unknown radiation was produced. Because of this, he believed the radiation was composed of atoms with a neutral electrical charge. This then became known as a neutron, because of this discovery an adequate model of an atom could be available to chemists. -
Bibliography
electron-and-nucleus [Accessed 15 Dec. 2019]. * Writer, E. (2019). Niels Bohr: Biography & Atomic Theory. [online] livescience.com. Available at: https://www.livescience.com/32016-niels-bohr-atomic-theory.html [Accessed 15 Dec. 2019]. * Physicsoftheuniverse.com. (2019). Niels Bohr - Important Scientists - The Physics of the Universe. [online] Available at: https://www.physicsoftheuniverse.com/scientists_bohr.html [Accessed 15 Dec. 2019]. -
Bibliography
Biography. (2019). Niels Bohr. [online] Available at: https://www.biography.com/scientist/niels-bohr [Accessed 15 Dec. 2019]. -
The modern atomic model
This new model updated the old model that showed that electrons were found on energy levels, this was actually not true. Instead, they are found in the electron cloud, The new model states that the atom is made of a small positively charged nucleus containing protons and neutrons surrounded by a cloudlike region of negatively charged electrons, this is called the electron cloud. -
Bibliography
*Writer, E. (2019). Niels Bohr: Biography & Atomic Theory. [online] livescience.com. Available at: https://www.livescience.com/32016-niels-bohr-atomic-theory.html [Accessed 15 Dec. 2019].
* Khan Academy. (2019). Discovery of the electron and nucleus. [online] Available at: https://www.khanacademy.org/science/chemistry/electronic-structure-of-atoms/history-of-atomic-structure/a/discovery-of-the-electron-and-nucleus [Accessed 15 Dec. 2019].
