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26.1 Properties of nucleus 26.2 Binding energy and mass defect.

is defined as the central core of an atom that is positively charged and contains protons and neutrons. UNIT 26 : NUCLEUS. (2 HOURS). 26.1 Properties of nucleus 26.2 Binding energy and mass defect. 26.1 Properties of nucleus (1/2 Hour). At the end of this topic, students should be able to:

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26.1 Properties of nucleus 26.2 Binding energy and mass defect.

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  1. is defined as the central core of an atom that is positively charged and contains protons and neutrons. UNIT 26 : NUCLEUS (2 HOURS) 26.1 Properties of nucleus 26.2 Binding energy and mass defect.

  2. 26.1 Properties of nucleus (1/2 Hour) At the end of this topic, students should be able to: • State the properties of proton and neutron • Define • Proton number • Nucleon number • Isotopes • Use to represent a nuclide

  3. 26.1 Properties of nucleus • A nucleus of an atom is made up of protons and • neutronsthat is also known asnucleons. Figure 26.1.2 (nucleus) Figure 26.1.1( atom)

  4. 26.1.1 Properties of proton and neutron Proton • Particle with positive charge of the nucleus • Charge : +1.60 x 10-19 C • Mass : 1.672 x 10-27 kg / 1.007276 u Neutron • Particle with no charge of the nucleus • Charge : - • Mass : 1.675 x 10-27 kg / 1.008665 u

  5. Proton number • Definition: the number of protons in the nucleus. • Also called as atomic number • Symbol : Z Nucleon number • Definition : the total number of neutrons and protons in the nucleus. • Also called as atomic mass number • Symbol : A Isotope • Definition : the atoms of the same element whose nuclei contain the same number of protons (Z) but different number of neutrons (N). • Example : (Hydrogen, deuterium, tritium)

  6. The atomic nucleus can be represented as where X = symbol for the element Z = atomic number (number of protons) A = atomic mass number = total number of protons and neutrons Example : Element : Iron-56 Proton no, Z = 26 Nucleon no, A = 56 Neutron = 56-26 = 30 A - Z = N

  7. Example 26.1 Complete the table below:

  8. 26.2 Binding energy & Mass Defect (1 1/2 Hour) At the end of this topic, students should be able to: • Define and determine mass defect • Define and determine binding energy, • Identify the average value of binding energy per nucleon of stable nuclei from the graph of binding energy per nucleon against nucleon number.

  9. 26.2.1 Mass defect, Δm Definition the difference between the sum of the masses of individual nucleons that form an atomic nucleus and the mass of the nucleus. Formula

  10. Example 26.2 From example above, can you determine the value of mass defect ? (Ans : 0.040475 a.m.u)

  11. 26.2.2 Binding Energy, EB Definition Energy required to separate a nucleus into its individual protons and neutrons. @ Energy released when nucleus is formed from its individual nucleons. Formula Where E : Binding energy Δm : Mass defect c : speed of light = 3.00 x 108ms-1

  12. There are 2 methods to determine the value of Binding Energy, EB • Example : Let Δm = 1 u = 1.66 x 10-27kg = Note : 1eV = 1.6 x 10-19J EB ( in unit J ) Δm ( in unit kg ) c = 3.00 x 108ms-1 EB ( in unit MeV ) Δm ( in unit u )

  13. Example 26.3 • Calculate • mass defect and • binding energy of the deuterium. • Given • Solution:

  14. Example 26.4 Calculate binding energy of the Helium nucleus, in SI unit. Given mass of helium atom = 4.002603 u Solution:

  15. 26.2.3 Binding Energy per nucleon, • Definition • mean (average) binding energyof a nucleus • Binding energy per nucleon is measure the stability of of the nucleus. • The greater the binding energy per nucleon, the more stable the nucleus is.

  16. Binding energy per nucleon as a function of mass number,A Greatest stability Binding energy per nucleon (MeV/nucleon) Mass number A

  17. From the graph: • For light nuclei the value of EB/A rises rapidly from 1 MeV/nucleon to 8 MeV/nucleon with increasing mass number A. • For the nuclei with A between 50 and 80, the value of EB/A ranges between 8.0 and 8.9 Mev/nucleon. The nuclei in these range are very stable. • The nuclide has the largest binding energy per nucleon (8.7945 MeV/nucleon). • For nuclei with A > 62, the values of EB/A decreases slowly, indicating that the nucleons are on average, less tightly bound. • For heavy nuclei with A between 200 to 240, the binding energy is between 7.5 and 8.0 MeV/nucleon.These nuclei are unstable and radioactive.

  18. Example 26.5 Calculate the average binding energy per nucleon of the iron-56 . Given Solution:

  19. Exercise The binding energy of the neon is160.64 MeV. Find its atomic mass. Given (Ans: 19.992u) Determine the total binding energy and the binding energy per nucleon for the nitrogen -14 nucleus Given (Ans:104.6 MeV,7.47 MeV/nucleon)

  20. 3) Calculate the binding energy of an aluminum nucleus in MeV. (Given mass of neutron, mn=1.00867 u ; mass of proton, mp=1.00782 u ; speed of light in vacuum, c=3.00108 m s1 and atomic mass of aluminum, MAl=26.98154 u) (Ans: 225 MeV) 4) Calculate the binding energy per nucleon of a boron nucleus in J/nucleon. (Given mass of neutron, mn=1.00867 u ; mass of proton, mp=1.00782 u ; speed of light in vacuum, c=3.00108 m s1 and atomic mass of boron, MB=10.01294 u) (E = 1.04x10 -12 J/nucleon)

  21. 5) Why is the uranium-238 nucleus is less stable than carbon-12 nucleus? Give an explanation by referring to the binding energy per nucleon. (Given mass of neutron, mn=1.00867 u ; mass of proton, mp=1.00782 u ; speed of light in vacuum, c=3.00108 m s1; atomic mass of carbon-12, MC=12.00000 u and atomic mass of uranium-238, MU=238.05079 u ) (Ans: U think) The end….. Next chapter : nuclear reaction

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