1. VIEWGRAPH SET # 4 THE ATOM AND THE NUCLEUS

2. Notes Note that elements 113, 115, and 117 are not known, but are included in the table to show their expected positions. There are unconfirmed reports for the observation of elements 114 (ununquadium), 116 (ununhexium), and 118 (ununoctium) and so these elements are also included. Note that the reports for 118 have been retracted, presumably maning 116 as well since that is a decay product of 118.

3. Atomic Mass Unit = 1.66x10 -27 kg Mass of one Carbon Atom =930 MeV/c 2 ISOTOPES -> same Z different A

4. BOHR THEORY Rules: 1.The atom has a number of stepped orbits that electrons that rotate at constant tangential velocity do not radiate (Stationary states or allowed orbits) 2. Electrons can jump from one allowed orbit to another with the emission or absorption of a photon with energy equal to their energy difference

6. All matter is an assembly of Atoms Stationary orbits of Hydrogen

7. Emission of photon. Electron moves from higher to lower allowed orbit Absorption of photon.Electron moves from lower to higher allowed orbit

8. Mathematics of Bohr atom Allowed or stationary Orbits for Hydrogen r n = n 2 a o a o =.5 x 10 -9 meters E n = - E o /n 2 E o = 13.6 eV n=1,2,3,… integer Allowed or stationary orbits for element with atomic number Z r n = n 2 a o /Z a o =.5 x 10 -9 meters E n = - Z 2 (E o /n 2 ) E o = 13.6 eV n=1,2,3,… integer Explain basic spectra of all atoms

9. Rare Earths Actinide

10. SHELL STRUCTURE OF ATOM Periodicity in physical and chemical properties of atoms (color, hardness, state –gas,liquid, density, heat and electric conduction,..) Magic numbers 2,8,8,18,18,32 Electrons are Fermions – spin 1/2 Pauli’s exclusion principle – Two Fermions cannot occupy the same state (cannot have the same address) Chemical properties of atoms controlled by the number of electrons in outer shell (valence electrons)

11. EnEn 2 6262 6 10 2 6 10 14 2 6262 6 10 2 n 654321654321 Left is number n of energy state Right is the maximum Number of electrons allowed on each level. They fill sequentially as we move from low Z, e.g Z=1 Hydrogen to higher Z. For example, Ca with Z=20 has filled The n=1,2,3 levels with18 electrons and has 2 electrons on the first Level of n=4. It has similar Properties with the elements that have 2 electrons on the First level of n=2 (Be), n=3 (Mg), n=5 (Sr), and n=6 (Ba) See periodic table group 2.

12. Radioactivityalpha decay Ra(226,88)->Rn(222,86)+He(4,2) U(238,92)->Th(234,90)+He(4,2) Beta decay C(14,6)->N(14,7)+e - +

14. Binding Energy: A nucleus is dismantled by removing a nucleon at a time and the amount of work done in the process is measured. Next if we next reassemble the nucleons in the form of the original nucleus, an amount of energy equal to the work done would be released. This is the called the binding energy of the nucleus. It indicates how tightly bound is. Key quantity is the binding energy per nucleon. It is the binding energy divided by the number of nucleons. Curve of the binding energy

17. DOUBLING TIMES Doubling time Growth factor 1 2 1 =2 2 2 2 =4 4 2 4 =16 10 2 10 =1024 25 3.3x10 7 50 1.1x10 15 80 1.2x10 24 Critical Mass Energy per U 235 fission 235 MeV