EDEXCEL CERTIFICATE IN PHYSICS 7-1 Atoms and Radioactivity

1. EDEXCEL CERTIFICATE IN PHYSICS 7-1Atoms and Radioactivity Edexcel IGCSE Physics pages 199 to 208

2. Edexcel Specification Section 7: Radioactivity and particles b) Radioactivity describe the structure of an atom in terms of protons, neutrons and electrons and use symbols such as 146C to describe particular nuclei understand the terms atomic (proton) number, mass (nucleon) number and isotope understand that alpha and beta particles and gamma rays are ionising radiations emitted from unstable nuclei in a random process describe the nature of alpha and beta particles and gamma rays and recall that they may be distinguished in terms of penetrating power describe the effects on the atomic and mass numbers of a nucleus of the emission of each of the three main types of radiation understand how to complete balanced nuclear equations

3. Atomic structure An atom consists of a small central nucleus composed of protons and neutrons surrounded by electrons. An atom will always have the same number of electrons as protons.

4. Atomic and mass number The atomic number of an atom is equal to the number of protons in its nucleus. The mass number of an atom is equal to the number of protons plus neutrons in its nucleus.

5. Properties of protons, neutrons and electrons

6. Nuclear notation

7. Isotopes The atoms of an element always have the same number of protons. Isotopes are atoms of the same element with different numbers of neutrons.

8. Question 1

9. Question 2

10. Radioactivity The atoms of some substances are unstable and they give out radiation from their nuclei all the time, whatever is done to them. These substances are said to be radioactive. The first three types of radiation discovered were alpha particles, beta particles and gamma rays.

11. Alpha, beta and gamma radiation An alpha particle is the same as a helium nucleus. It consists of two protons and two neutrons. A beta particle is a high speed electron. It has come from the nucleus where a neutron has decayed into an electron and proton. Gamma rays are very high frequency electromagnetic waves. They are produced when an unstable nucleus loses energy.

12. The penetrating power of alpha, beta and gamma radiation

14. Simulations Build an atom - eChalk Atomic Structure Quiz - by KT - Microsoft WORD Hidden Pairs Game on Atomic Structure - by KT - Microsoft WORD Types of Radiation - S-Cool section on types of radiations including an animation of absorption and a couple of decay equations to fill in on screen. Andy Darvill's Radioactivity Pages Understanding Radiation - National Radiological Protection Board - Useful starting point to get at useful areas of the site. BBC Bitesize Revision: Introduction Page to AQA Radioactive Substances Atoms & Isotopes Alpha, beta & gamma radiation - what they are Penetrating power of radiations - includes applet - also see page on detecting radiations (two after)

15. Ionisation Ionisation occurs when an atom loses one or more of its electrons. The atom becomes a positive ion. Alpha particles cause intense ionisation due to their large mass double positive charge. Beta particles cause moderate ionisation. Gamma rays only cause weak ionisation because they are uncharged.

16. Deflection by magnetic fields

17. Deflection by electric fields

19. Alpha decay Alpha particles consist of two protons plus two neutrons. They are emitted by some of the isotopes of the heaviest elements.

20. Example: The decay of Uranium 238

21. Question

22. Beta decay Beta particles consist of high speed electrons. They are emitted by isotopes that have too many neutrons. One of these neutrons decays into a proton and an electron. The proton remains in the nucleus but the electron is emitted as the beta particle.

23. Example: The decay of Carbon 14

24. Question

25. Gamma decay Gamma decay is the emission of electromagnetic radiation from an unstable nucleus Gamma radiation often occurs after a nucleus has emitted an alpha or beta particle. Example: Cobalt 90

26. Changing elements Both alpha and beta decay cause the an isotope to change atomic number and therefore element. Alpha decay also causes a change in mass number.

27. Complete the decay equations below:

28. Write equations showing how Lead 202 could decay into Gold. (This cannot happen in reality!)

30. Simulations Types of Radiation - S-Cool section on types of radiations including an animation of absorption and a couple of decay equations to fill in on screen. Andy Darvill's Radioactivity Pages Understanding Radiation - National Radiological Protection Board - Useful starting point to get at useful areas of the site. BBC Bitesize Revision: Alpha, beta & gamma radiation - what they are Penetrating power of radiations - includes applet - also see page on detecting radiations (two after) Deflecting radiations using electric and magnetic fields - includes applets showing deflections Detecting radiation using photographic film (badges) & GM tube - includes applet testing penetrating power with GM tube detector Hazards of radiation

31. Simulations Various Radioactive Materials in the Home - 'Whys Guy' Video Clip (4:30mins) Andy Darvill's Radioactivity Pages Understanding Radiation - National Radiological Protection Board - Useful starting point to get at useful areas of the site. Radon Gas - National Radiological Protection Board BBC Bitesize Revision: Using radiation - tracers & thickness measurement - includes applet showing sheet rolling application Test bite on Radioactive Sources

32. Atoms and RadioactivityNotes questions from pages 199 to 208 Answer the questions on pages 207 and 208. Verify that you can do all of the items listed in the end of chapter checklist on page 207.

33. Online Simulations