It is not necessarily a true picture of the exact structure of an atom. Models are often simplified. The small toy cars that you may have played with as a child are models. They give you a good idea of what a real car looks like, but they are much smaller and much simpler. A model cannot always be absolutely accurate and it is important that we realise this, so that we do not build up an incorrect idea about something. John Dalton proposed that all matter is composed of very small things which he called atoms.
Niels Bohr Facts for Kids
This was not a completely new concept as the ancient Greeks notably Democritus had proposed that all matter is composed of small, indivisible cannot be divided objects. When Dalton proposed his model electrons and the nucleus were unknown. After the electron was discovered by J. Thomson in , people realised that atoms were made up of even smaller particles than they had previously thought.
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In , Thomson was awarded the Nobel Prize for his work in this field. However, even with the Plum Pudding Model, there was still no understanding of how these electrons in the atom were arranged.
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The discovery of radiation was the next step along the path to building an accurate picture of atomic structure. In the early twentieth century, Marie and Pierre Curie, discovered that some elements the radioactive elements emit particles, which are able to pass through matter in a similar way to X—rays read more about this in Grade It was Ernest Rutherford who, in , used this discovery to revise the model of the atom.
Two other models proposed for the atom were the cubic model and the Saturnian model.
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In the cubic model, the electrons were imagined to lie at the corners of a cube. In the Saturnian model, the electrons were imagined to orbit a very big, heavy nucleus. Rutherford carried out some experiments which led to a change in ideas around the atom. His new model described the atom as a tiny, dense, positively charged core called a nucleus surrounded by lighter, negatively charged electrons.
Another way of thinking about this model was that the atom was seen to be like a mini solar system where the electrons orbit the nucleus like planets orbiting around the sun.
Niels Bohr facts for kids
A simplified picture of this is shown alongside. This model is sometimes known as the planetary model of the atom. There were, however, some problems with Rutherford's model: for example it could not explain the very interesting observation that atoms only emit light at certain wavelengths or frequencies. Niels Bohr solved this problem by proposing that the electrons could only orbit the nucleus in certain special orbits at different energy levels around the nucleus. Rutherford predicted in that another kind of particle must be present in the nucleus along with the proton.
He predicted this because if there were only positively charged protons in the nucleus, then it should break into bits because of the repulsive forces between the like-charged protons!
To make sure that the atom stays electrically neutral, this particle would have to be neutral itself. In James Chadwick discovered the neutron and measured its mass.
What Is Bohr’s Atomic Model?
Bohr would come to apply this idea philosophically as well, with the belief that evolving concepts of physics deeply affected human perspectives. Bohr went on to work with the group of scientists who were at the forefront of research on nuclear fission during the late s, to which he contributed the liquid droplet theory.
Outside of his pioneering ideas, Bohr was known for his wit and warmth, and his humanitarian ethics would inform his later work. With Adolf Hitler's rise in power, Bohr was able to offer German Jewish physicists refuge at his institute in Copenhagen, which in turn led to travel to the United States for many. Once Denmark became occupied by Nazi forces, the Bohr family escaped to Sweden, with Bohr and his son Aage eventually making their way to the United States.
Because he had concerns about how the bomb could be used, he called for future international arms control and active communication about the weapon between nations—an idea met with resistance by Winston Churchill and Franklin D.
After the end of the war, Bohr returned to Europe and continued to call for peaceful applications of atomic energy. In his "Open Letter to the United Nations," dated June 9, , Bohr envisioned an "open world" mode of existence between countries that abandoned isolationism for true cultural exchange.
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In , Bohr received the Atoms for Peace Award for his trailblazing theories and efforts to use atomic energy responsibly. Bohr was a prolific writer with more than publications to his name. After having a stroke, he died on November 18, , in Copenhagen. We strive for accuracy and fairness.
If you see something that doesn't look right, contact us! Sign up for the Biography newsletter to receive stories about the people who shaped our world and the stories that shaped their lives. Physicist Enrico Fermi built the prototype of a nuclear reactor and worked on the Manhattan Project to develop the first atomic bomb. Thomson was a Nobel Prize winning physicist whose research led to the discovery of electrons. Albert Einstein was a German-born physicist who developed the general theory of relativity.