-
John Dalton
John Dalton was born on 6 September 1766. He is best known for proposing the modern atomic theory. -
John Dalton, Contributions
John Dalton's theory contained the following points
Elements are made of extremely small particles called atoms.
Atoms of a given element are identical in size and mass; atoms of different elements differ in size and mass.
Atoms cannot be divided, created, or destroyed.
Atoms of different elements combine in simple whole-number ratios to form chemical compounds.
In chemical reactions, atoms are combined, separated, or rearranged. -
John Dalton, Shortcomings
he indivisibility of an atom was proved wrong: an atom can be further subdivided into protons, neutrons and electrons. However an atom is the smallest particle that takes part in chemical reactions.
According to Dalton, the atoms of same element are similar in all respects. However, atoms of some elements vary in their masses and densities. These atoms of different masses are called isotopes. For example, chlorine has two isotopes with mass numbers 35 and 37. -
John Dalton, Shortcomings
Dalton claimed that atoms of different elements are different in all respects. This has been proven wrong in certain cases: argon and calcium atoms each have an atomic mass of 40 amu. These atoms are known as isobars.
According to Dalton, atoms of different elements combine in simple whole number ratios to form compounds. This is not observed in complex organic compounds like sugar (C12H22O11). -
Maria Mitchell
Maria Mitchell was born on August 1, 1818 in 1847, by using a telescope, discovered a comet, which as a result became known as "Miss Mitchell's Comet. She won a gold medal prize for her discovery, which was presented to her by King Frederick VI of Denmark. -
Maria Mitchell, Contributions
Maria Mitchell is best known for being the first professional female astronomer in the United States. She discovered a new comet in 1847 that became known as "Miss Mitchell's Comet." -
JJ Thomson
JJ Thomson was born on December 18, 1856. Thomson was in charge of the discovery of the electron; and with the discovery of the first subatomic particle. -
Marie Curie
Marie Curie was born on November 7, 1867 she conducted pioneering research on radioactivity. She was the first woman to win a Nobel Prize, the first person and only woman to win twice, the only person to win a Nobel Prize in two different sciences. -
Ernest Rutherford
Ernest Rutherford was born on August 30, 1871; he was known as the father of nuclear physics. -
Lise Meitner
Lise Meitner was born on November 7, 1878, she worked on radioactivity and nuclear physics. Meitner led the small group of scientists who first discovered nuclear fission of uranium when it absorbed an extra neutron. -
Niels Bohr
Niels Bohr was born on October 7, 1885 he made to understanding atomic structure and quantum theory, he received the Nobel Prize in Physics in 1922. -
James Chadwick
James Chadwick was born on October 20, 1891, he was awarded the 1935 Nobel Prize in Physics for his discovery of the neutron in 1932. He was the head of the British team that worked on the Manhattan Project during the Second World War. -
JJ Thomson, Contributions
In 1897, Thomson showed that cathode rays were composed of previously unknown negatively charged particles, which he calculated must have bodies much smaller than atoms and a very large value for their charge-to-mass ratio. Thomson is also credited with finding the first evidence for isotopes of a stable (non-radioactive) element in 1913, as part of his exploration into the composition of canal rays (positive ions). -
JJ Thomson, Shortcomings
Rutherford's gold foil experiment of scattering α-particles revealed that most of the space in an atom is empty contradicted Thomson's atomic model. Thus, it was found that the plum pudding atomic model was insufficient to explain the structure of an atom. -
Enrico Fermi
Enrico Fermi September 29, 1901 he created of the world's first nuclear reactor, the Chicago Pile-1. Fermi held several patents related to the use of nuclear power, and was awarded the 1938 Nobel Prize in Physics for his work on induced radioactivity by neutron bombardment and the discovery of transuranic elements. -
Grace Hopper
Grace Hopper was born on December 9, 1906 she was an American computer scientist and United States Navy rear admiral. One of the first programmers of the Harvard Mark I computer, she invented one of the first compiler related tools. She popularized the idea of machine-independent programming languages, which led to the development of COBOL, an early high-level programming language still in use today. -
Ernest Rutherford, Contributions
In 1911, although he could not prove that it was positive or negative, he theorized that atoms have their charge concentrated in a very small nucleus. He conducted research that led to the first "splitting" of the atom in 1917 in a nuclear reaction between nitrogen and alpha particles, in which he also discovered (and named) the proton. -
Niels Bohr, Contributions
In 1911, Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another. -
Ernest Rutherford, Shortcomings
A major fraction of the α-particles bombarded towards the gold sheet passed through it without any deflection, and hence most of the space in an atom is empty.
Some of the α-particles were deflected by the gold sheet by very small angles, and hence the positive charge in an atom is not uniformly distributed. The positive charge in an atom is concentrated in a very small volume. -
Niels Bohr, Shortcomings
The first wrong assumption made by Bohr is considering the electron orbiting around the nucleus in a circular orbit, however, we know now that this is not correct, because electrons exist in a cloud.
Bohr model is valid only for hydrogen since it has one electron only, however, when it was applied to other elements, the experimental data were different than the theoretical calculations. -
James Chadwick, Contributions
Chadwick is best known for his discovery of the neutron in 1932. A neutron is a particle with no electric charge that, along with positively charged protons, makes up an atom's nucleus. -
Marie Curie, Shortcomings
Marie Curie died in 1934, aged 66, at a sanatorium in Sancellemoz (Haute-Savoie), France, of aplastic anemia from exposure to radiation in the course of her scientific research and in the course of her radiological work at field hospitals during World War I -
Lise Meitner, Contributions
Meitner results for nuclear fission of uranium were published in early 1939. Meitner understood that the fission process, which splits the atomic nucleus of uranium into two smaller nuclei, must be accompanied by an enormous release of energy. This process is the basis of the nuclear weapons that were developed in the U.S. during World War II and used against Japan in 1945. Nuclear fission is also the process exploited by nuclear reactors to generate electricity -
Enrico Fermi, Contributions
Enrico Fermi built the prototype of a nuclear reactor and worked on the Manhattan Project to develop the first atomic bomb. On December 2, 1942, 49 scientists, led by Enrico Fermi, made history when Chicago Pile 1 (CP-1) went critical and produced the world's first self-sustaining, controlled nuclear chain reaction. -
Lise Meitner, Shortcomings
In 1945, the Royal Swedish Academy of Sciences awarded the Nobel Prize in Chemistry to Otto Hahn for the discovery of nuclear fission, overlooking the physicist Lise Meitner, who collaborated with him in the discovery and gave the first theoretical explanation of the fission process. -
Grace Hopper, Contributions
Grace believed that computer code could be written in English by using a programming language that was based on English words. The compiler would convert that code into machine code that would be understood by computers. By 1952, Hopper finished her compiler, which was written for the A-0 System programming language. -
Grace Hopper, Shortcomings
Hopper had attempted to enlist in the Navy during World War II, but she was rejected by the military because she was 34 years of age and too old to enlist. -
Marie Curie, Contributions
Marie's achievements included the development of the theory of radioactivity, techniques for isolating radioactive isotopes, and the discovery of two elements, polonium and radium, the world's first studies into the treatment of neoplasms, using radioactive isotopes. During World War I, she developed mobile radiography units to provide X-ray services to field hospitals. -
Sources
https://en.wikipedia.org/wiki/Enrico_Fermi
http://chemed.chem.purdue.edu/genchem/history/dalton.html
https://en.wikipedia.org/wiki/John_Dalton
https://en.wikipedia.org/wiki/J._J._Thomson
https://en.wikipedia.org/wiki/Ernest_Rutherford
https://en.wikipedia.org/wiki/Lise_Meitner
https://en.wikipedia.org/wiki/Niels_Bohr
https://en.wikipedia.org/wiki/James_Chadwick
https://www.atomicheritage.org/profile/james-chadwick
https://en.wikipedia.org/wiki/Grace_Hopper -
Sources
https://en.wikipedia.org/wiki/Marie_Curie
https://www.iupac.org/publications/ci/2011/3301/5_adloff.html
https://en.wikipedia.org/wiki/Enrico_Fermi
https://www.biography.com/people/enrico-fermi-9293405
http://www.ne.anl.gov/About/cp1-pioneers/
https://en.wikipedia.org/wiki/Maria_Mitchell
https://www.biography.com/people/maria-mitchell-9410353
https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Atomic_Theory/Dalton%
27s_Atomic_Theory/Postulates_of_Dalton%27s_Atomic_Theory -
Sources
https://image.slidesharecdn.com/thedevelopmentoftheatomictheory-131124015429-phpapp01/95/the-development-of-the-atomic-theory-5-638.jpg?cb=1385259015
https://www.biography.com/.image/t_share/MTIwNjA4NjMzOTE2NjU1MTE2/maria-mitchell-9410353-1-402.jpg
https://mir-s3-cdn-cf.behance.net/project_modules/1400/1bf75f29962329.560c462b42e75.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/5/57/Signature_Marie_Curie.svg/2000px-Signature_Marie_Curie.svg.png -
Sources
http://www.writersreserve.com/wp-content/uploads/SIGNATURE-Ernest-Rutherford-Lord.png
https://upload.wikimedia.org/wikipedia/commons/thumb/a/ae/Lise_Meitner_signature.svg/2000px-Lise_Meitner_signature.svg.png
https://upload.wikimedia.org/wikipedia/commons/thumb/d/d3/Niels_Bohr_Signature.svg/2000px-Niels_Bohr_Signature.svg.png
https://s3-eu-west-1.amazonaws.com/lot-images.atgmedia.com/SR/35396/2914032/494-201494113856_540x360.jpghttp://study.com/cimages/multimages/16/thomsonexperiment2.png -
Sources
https://upload.wikimedia.org/wikipedia/commons/thumb/f/fc/Enrico_Fermi_signature.svg/2000px-Enrico_Fermi_signature.svg.png
https://image.slidesharecdn.com/qojt0astrmissb5pjwsk-signature-058a17ca7a5ddf179a70c58a4ea22a49fb0adc33f57a18223ab73549597c23c5-poli-150702163334-lva1-app6891/95/grace-brewster-murray-hopper-5-638.jpg?cb=1435870703
http://chemed.chem.purdue.edu/genchem/history/gifs/fig6_13.gifhttps://d2gne97vdumgn3.cloudfront.net/api/file/7QVkA9IeSe04Zmr1SdGP -
Sources
https://sites.google.com/site/chadwickexperiment/_/rsrc/1255200152958/home/exp2.jpg
https://rampages.us/mccourtee/wp-content/uploads/sites/8694/2016/02/lise-photo.jpg
https://www.atomicheritage.org/sites/default/files/Graphite%20Layers%202.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/3/37/Grace_Hopper_and_UNIVAC.jpg/220px-Grace_Hopper_and_UNIVAC.jpg
https://upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Pierre_and_Marie_Curie.jpg/800px-Pierre_and_Marie_Curie.jpg -
Sources
https://byjus.com/chemistry/j-j-thomsons-atomic-model-and-its-limitations/
https://byjus.com/chemistry/rutherfords-model-of-atoms-and-its-limitations/
https://www.sdsc.edu/ScienceWomen/meitner.html
https://socratic.org/questions/what-are-two-major-shortcomings-of-the-bohr-model-of-the-atom-1
https://upload.wikimedia.org/wikipedia/commons/thumb/2/2c/John_Dalton_Signature_c1827.svg/1024px-John_Dalton_Signature_c1827.svg.png
