Radioactive decay mechanisms and radioisotopes

1. Radioactive decay mechanisms and radioisotopes Exam question Decay mechanisms Radio isotopes

2. Decay mechanisms next previous smart

3. An alpha particle is really four particles which are ejected from the nucleus of an unstable atom. An alpha particle is two protons and two neutrons. next previous smart

4. Np 237 93 What happens when atoms of emit alpha particles? Notice that it is impossible to predict which atoms will decay but we can see that the rate of decay slows down with time. We will now look deeper inside the atom to see what is happening to the nucleus. This is a model to simulate how ALPHA particles are emitted from a radioactive isotope of NEPTUNIUM. next previous smart

5. Taking a closer look inside the NEPTUNIUM atom loses 2 protons and 2 neutrons which we call an alpha particle The nucleus next previous smart

6. 237 Np Pa + 93 91 Palladium alpha Neptunium + Before After Fill in the missing numbers to complete the equation next previous smart

7. 237 233 4 Np Pa + 93 2 91 Palladium alpha Neptunium + Before After answers next previous smart

8. A beta particle is simply a fast moving electron. This particle is also ejected from the nucleus of an unstable atom but the way this happens is more complicated than alpha emission. next previous smart

9. 233 Pa 91 What happens when atoms emit beta particles? Notice that it is impossible to predict which atoms will decay but we can see that the rate of decay slows down with time. We will now look deeper inside the atom to see what is happening to the nucleus. This is a model to simulate how BETA particles are emitted from a radioactive isotope of PALLADIUM. next previous smart

10. Taking a closer look inside the PALLADIUM atom emits a beta particle when a neutron changes into a proton and an electron The nucleus next previous smart

11. B 233 0 Pa U + 91 -1 Uranium Beta Palladium + Before After Fill in the missing numbers to balance the equation next previous smart

12. B 233 0 Pa 233 U + 91 -1 92 Uranium Beta Palladium + Before After answers next previous smart

13. Gamma rays are really electromagnetic rays which are given out by the nucleus of unstable atoms. You will not need to know how this affects the nucleus of an unstable atom. next previous smart

14. Exam question next previous smart

15. 145 Number of neutrons 237 Neptunium-237 ( Np) is a radioactive element. The graph shows the numbers of neutrons and protons in the nuclei of the elements formed when Np decays. 237 Np 237 233 Pa 229 Th 233 U 144 143 142 141 140 139 138 137 X Number of protons 136 87 88 89 90 91 92 93 94 next previous smart

16. 145 • Use the periodic table • to identify element X. (c) What type of radiation is released when Np decays to form Pa? 237 233 233 (b) Why are Pa and U considered to be different elements? 233 237 Np 233 Pa 229 Th 233 U (d) What change takes place in the nucleus when Pa changes into U? 233 233 Number of neutrons 144 143 142 141 140 139 138 137 X 136 Number of protons 87 88 89 90 91 92 93 94 next previous smart

17. 145 237 Np 233 Pa 229 Th 233 U • Use the periodic table • to identify element X. Number of neutrons 144 143 142 141 140 139 138 137 X Number of protons 136 87 88 89 90 91 92 93 94 next previous smart

18. 145 237 Np 233 Pa 229 Th 233 U 233 (b) Why are Pa and U considered to be different elements? 233 Number of neutrons 144 143 142 Pa has 91 protons 141 140 U has 92 protons 139 Different proton number means different element. 138 137 X Number of protons 136 87 88 89 90 91 92 93 94 next previous smart

19. 145 (c) What type of radiation is released when Np decays to form Pa? 237 233 237 Np 233 Pa Number of neutrons 144 143 142 The nucleus of Neptunium has lost 2 neutrons 141 and 2 protons. 140 Neptunium nucleus Pa nucleus 139 138 Number of protons 137 136 Alpha particle 87 88 89 90 91 92 93 94 next previous smart

20. 145 237 Np 233 Pa 233 U Number of neutrons 144 (d) What change takes place in the nucleus when Pa changes into U? 143 233 233 142 The neutron number decreases by one 141 but the proton number increases by one 140 139 A neutron changes into a proton and an electron 138 137 Number of protons 136 87 88 89 90 91 92 93 94 next previous smart

21. Radio Isotopes next previous smart

22. Definition An isotope is an atom which has the same number of protons but a different number of neutrons The underlined phrases score the marks---so learn this definition off by heart next previous smart

23. Nucleon number A X Symbol of the element Proton number Z 7 1 12 Li H C 3 1 6 next previous smart

24. You should know what an isotope is What a radio-isotope is and give some examples. next previous smart

25. H H H Write in the missing numbers (the bottom one is the number of protons) (the top one is the protons and neutrons) next previous smart

26. 1 2 3 H H H 1 1 1 answers next previous smart

27. He He next previous smart

28. 4 3 He He 2 2 answers next previous smart

29. 12 14 C C 6 6 Now lets have a closer look at the nuclei of these isotopes. next previous smart

30. C C N Count the particles in these nuclei after the beta particle is emitted and fill in the numbers Carbon-12 is stable but Carbon-14 is unstable (a radio-isotope). Carbon-14 emits a beta particle and decays to become nitrogen next previous smart

31. 12 14 N C 7 6 answers Carbon-12 is stable but Carbon-14 is unstable (a radio-isotope). Carbon-14 emits a beta particle and decays to become nitrogen next previous smart

32. END previous