Niels Bohr

1. Niels Bohr By Alex Joslyn Timothy Boualapha Blayne Michalski Natalie VonAchen Zachary Giaconne

2. Neils Bohr�s Background Born October 7, 1885 in Copenhagen, Denmark Studied as an undergraduate under Christian Christiansen at Copenhagen University He received his doctorate 1911 Won the 1922 Noble Prize for physics for his work on the atomic structure

3. Background Continued�. Became a professor of physics at the University of Copenhagen in 1916 Received the Royal Society Copley Medal in 1938 During WWII, he went to New Mexico to warn scientists of what the atomic bomb was capable of Died on November 18, 1962 at the age of 77

4. Prediction In 1913, he published a theory about the structure of the atom based on an earlier theory of Rutherford Bohr�s theory proposed that electrons travel in only certain circular orbits Predicted that the outer orbits of an atom could hold more electrons than the inner ones Proposed the number of electrons in the outer orbits determine the atom's chemical properties

5. Prediction Continued�. Proposed that hydrogen has only certain allowable energy sates The lowest (ground state) is when an atom has little energy The highest (excited state) is when atom has the most energy When an atom absorbs or gives off energy , the electron jumps to higher or lower orbits Emission: To release or give off

6. Evidence/Experimental Design To prove his theory he assigned a number n to each orbit This number was referred to as a quantum number Quantum Number: a number assigned to each orbit of an electron He then calculated the radius of each orbit

7. Evidence/Experimental Design Continued� Example- For the first orbit, the electron closet to the nucleus: n=1 The radius was 0.0529 nm

8. Evidence/Experimental Design Continued� To prove electrons jump to higher or lower orbits he created a model It states that an atom is in a ground state when n =1 and does not radiate energy Also, when energy is added to an atom, the electron moves to a higher-energy orbit, such as n =2

9. After Bohr�s Findings Even though Bohr�s model explained hydrogen�s orbit, it did not explain any other elements However, his findings did allow other physicists to expand on his findings into creating quantum mechanics Quantum Mechanics: a theory of the mechanics of atoms, molecules, and other physical systems that are subject to the uncertainty principle

10. Works Cited http://www2.lucidcafe.com/lucidcafe/library/95oct/nbohr.html http://www.pbs.org/wgbh/aso/databank/entries/dp13at.html Zike, Dinah. Chemistry Matter and Change. Columbus: Glencoe, 2008. (110, 146)