https://padlet.com/4000223081/2knkqhkynrskk2g3 en-us 2021-09-14 15:20:38 UTC 2025-11-02 02:13:55 UTC hello@padlet.com https://padlet.net/icons/png/1f3c0.png 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743109130 Scientist: Democritus (Greek Philosopher)
Timeline: 400 BC Democritus was
the first person to use the term atom or atomos; meaning indivisible. He thought that if you take a piece of matter and divide it and continue to divide it you will eventually, come to a point where you could not divide it anymore. ]]> 2021-09-15 15:14:12 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743109130 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743127718 Scientist: Aristotle (Greek philosopher)
Timeline:  384 BC Aristotle was one of the first genuine scientists in history. He made introduce contributions to all fields of philosophy and science. He invented the field of formal logic, and he identified the various scientific disciplines and explored their relationships with each other. He thought that all materials on Earth were not made of atoms, but of the four elements, Earth, Fire, Water, and Air. He believed all substances were made of small amounts of these four elements of matter.]]> 2021-09-15 15:19:25 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743127718 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743149768 Scientist: John Dalton 
Timeline: 1800’s John Dalton was the first to adapt Democritus’ theory into the first modern atomic All matter consists of tiny particles called atoms. Some of his theories were atoms are indestructible and unchangeable; elements are characterized by the weight of their atoms; when elements react, it is their atoms that have combined to form new
compounds

]]> 2021-09-15 15:25:29 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743149768 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743153717 Scientist: Sir William Crooke
Timeline: 1861 Sir William Crooke was a British chemist and physicist. Mr. Crookes discovered thallium by observing the prominent green spectral line generated by selenium-bearing pyrites that had been used in the manufacture of sulfuric acid. Crookes and French chemist Claude-Auguste Lamy independently isolated thallium, showing it to be a metal.]]> 2021-09-15 15:26:36 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743153717 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743175510 Scientist: J.J Thomson
Timeline: 1890’s J.J Thomson was a physicist who is credited for discovering the electron. He used his research on cathode ray tube technology in this discovery. when he had found this negative charge. Through a series of clever experiments, he was able to predict the mass of this charge.  He then found out that this charge was 1000 times lighter than a hydrogen atom. He made a bold statement saying that this negative charge must be inside an atom. This negative charge (he called
corpuscles) later became known as the electron. ]]> 2021-09-15 15:32:50 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743175510 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743186550 Scientist: Ernest Rutherford
Timeline: 1910’s Ernest Rutherford was not convinced about the model of the atom proposed by Thomson. He thus set up his now-famous ¨Gold Foil Experiment¨ in 1908. He fired alpha particles (positively charged) at a gold foil. He measured the deflection as the particles came out the other side. Most of the particles did not deflect at all. Every now and then a particle would deflect all the way back. He said that there must be a positive center of the foil. He called this center the nucleus. ]]> 2021-09-15 15:36:12 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743186550 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743299248 Scientist: Sir James Chadwick
Timeline: 1930ś Chadwick made a fundamental discovery in the domain of nuclear science: he proved the existence of neutrons – elementary particles devoid of any electrical charge. In 1932, the physicist James Chadwick conducted an experiment in which he bombarded Beryllium with alpha particles from the natural radioactive decay of Polonium.
 In this way, Chadwick's findings were pivotal to the discovery of nuclear fission, and ultimately the development of the atomic bomb.]]> 2021-09-15 16:12:42 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743299248 4000223081 https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743307931 Scientist: Niels Bohr
Timeline: 1910’s Niels Bohr agreed with the planetary model of
the atom, but also knew that it had a few flaws. Using his knowledge of energy and quantum physics he was able to perfect Rutherford’s model. He was able to answer why the electrons did not collapse into the nucleus. Electrons orbit the nucleus in orbits that have a set size and energy. The lower the energy of the electron, the lower the orbit. This means that as electrons fill up the orbitals, they will fill the lower energy level first. If that energy level is fill (or at capacity), a new energy level will begin. Radiation is when an electron moves from one level to another. The problems with this theory: Electrons do not travel on a specific orbit or path]]> 2021-09-15 16:15:47 UTC https://padlet.com/4000223081/2knkqhkynrskk2g3/wish/1743307931