1. The Atom Lab # 2

3. What’s Inside an Atom? An atom is made up of a team of three players: protons, neutrons, and electrons They each have a charge, mass, and a location Protons + Neutrons collectively called nucleons

4. What is the structure of an atom? Nucleus – center of the atom –Home of Protons and Neutrons –Proton Has a positive (+) charge Has a relative mass of 1 Determines the atomic number Found inside the nucleus

5. What is the structure of an atom? –Neutron Has no charge (0) Has a relative mass of 1 Found inside the nucleus

6. What is the structure of an atom? Electron –Has a negative (-) charge –Has a relative mass of 0 (zero) –Determines the ion –Found outside the nucleus

7. Electrons circle around the nucleus of an atom. Protons are a main part of the nucleus of an atom. Neutrons also hang out in the nucleus of an atom.

9. How are P, N, e - related? # protons = atomic number = Z # electrons = # protons in a neutral atom # protons + # neutrons = mass number = A –Ex: The atomic number of Hydrogen (H) is 1, so all hydrogen atoms have 1 proton. –Ex: All Oxygen atoms (O) have 8 protons, so the atomic number of Oxygen is 8. Remember all atoms are electrically neutral. Therefore; the number of Protons equal the number of Electrons. Meaning the number of negatively charged particles must equal the number of postively charged particles. –Ex: Helium (He) has 2 protons and 2 neutrons: its mass number is 4. –Ex: Carbon (C) has 6 protons and 6 neutrons: its mass number is12.

10. A X ZN # protons + # neutrons = mass number = A # protons = atomic number = Z # neutrons Structure of the Nucleus

11. A Al 1314 27 Structure of the Nucleus

12. Some 3000 nuclides have been discovered and most are unstable. Unstable nuclei decay by one of the following in order to achieve stability –spontaneous fission –α-particle –β-particle –σ-ray emission –Electron capture Decay of Radionuclides

13. The stability of a nuclide is governed by the structural arrangement and binding energy of the nucleons in the nucleus. The ratio of the number of neutrons to the number of protons N/Z is an approximate index of the stability of a nuclide. N/Z = 1 in the stable nuclei with low atomic no. Ex, C 6 12 Decay of Radionuclides

14. Radionuclides may decay by any one or a combination of six processes: –Spontaneous fission –α decay –β- decay –‏β+decay –Electron capture –Isomeric transition

15. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –Spontaneous fission Fission is a process in which a heavy nucleus breaks down into two fragments typically in the ratio of 60:40. This process is accompanied by the emission of Two or three neutrons with a mean energy of 1.5 MeV. A release of 200 MeV energy appears mostly as heat. Fission in heavy nuclei can occur spontaneously or by bombardment with energetic particles. Spontaneous fission is an alternative to a decay or g emission

16. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –α decay Usually heavy nuclei decay by α particle emission. The α particle is a helium ion containing two protons and two neutrons bound together in the nucleus. In α particle the atomic number of the parent nuclide is therefore reduced by 2 and the mass number by 4. An example of a decay is

17. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –β- decay When a nucleus is ‘‘neutron rich’’ it decays by β- particle emission along with an antineutrino. An antineutrino is an entity almost without mass and charge and is primarily needed to conserve energy in the decay. In β- decay, a neutron essentially decays into a proton (p) and a β- particle For example (i.e., has a higher N/Z ratio compared to the stable nucleus)

18. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –β- decay

19. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –Positron or β+decay Nuclei that are ‘‘neutron deficient’’ or ‘‘proton rich’’ can decay by β+ particle emission accompanied by the emission of a neutrino which is an opposite entity of the antineutrino. After β+ particle emission, the daughter nuclide has an atomic number that is 1 less than that of the parent. In β+ decay, a proton transforms into a neutron by emitting a β+ particle and a neutrino For example, (i.e., have an N/Z ratio less than that of the stable nuclei)

20. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –β+ decay

21. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –Electron capture Electron is captured from the extranuclear electron shells. Thus, transforming a proton into a neutron and emitting a neutrino.

22. Decay of Radionuclides Radionuclides may decay by any one or a combination of six processes: –Isomeric transition The decay of an upper excited state to a lower excited state A nucleus can remain in several excited energy states above the ground state. All these excited states are referred to as isomeric states and decay to the ground state

23. Nomenclature Isotopes: Nuclides of the same atomic number. O O O Isotones: Nuclides having the same number of neutrons but different atomic number Fe Co Cu Isobars: Nuclides with the same no. of nucleons that is the same mass no. but different no. of protons Cu Zn Isomers: Nuclides having the same number of protons and neutrons but differing in energy states and spins. 99Tc 99mTc 8 15 8 16 8 17 26 59 60 62 27 29 67 3029

24. Units of Radioactivity 1 curie (Ci) = 3.7 X 10 10 dps = 2.22 X 10 12 dpm 1 millicurie (mCi) = 3.7 X 10 7 dps = 2.22 X 10 9 dpm 1 microcurie (µCi) = 3.7 X 10 4 dps = 2.22 X 10 6 dpm

25. 1 Becquerel (Bq)= 1 dps = 2.7 X 10 -11 Curie 1 kilobecquerel (kBq)= 2.7 X 10 -8 Curie 1 Ci = 3.7 X 10 10 Becquerel (Bq) Units of Radioactivity

26. Decay Equations -dN/dt=λN –λLambda= decay constant. –Defined as the probability of disintegration per unit time for the radioactive atom –-dN/dt = A =disintegration rate –N is the no. of radioactive atoms At = A o e- λt A=λN λ=0.693/t1/2 –t1/2 = the time required to reduce the initial activity of a radionuclide to one half

27. Problems 1.At 11:00 A.M., the 99mTc readioactivity was measured as 9 mCi on a certain day. What was the activity at 8:00 A.M. and 4:00 P.M. on the same day (t1/2 of 99mTc= 6hr)

28. Thank You “Instead of giving yourself reasons why you can’t, give yourself reasons why you can”