Radioactivity C17 Worksheet Notes

5105 Science (Physics) Chapter 17 | Radioactivity 1 Name: _________________________________________TG: ______ Date: ___________ Chapter 17: Radioactivity Content: • The composition of the atom • Radioactive decay • Dangers and uses of radioactivity Learning Outcomes: Candidates should be able to: (a) describe the composition of an atom in terms of a positively charged nucleus (with protons and neutrons) and negatively charged electrons (b) use the terms proton (atomic) number Z, nucleon (mass) number A and isotope (c) use and interpret the term nuclide and use the nuclide notation 𝑋𝑍 𝐴 (d) show an understanding that nuclear decay is a random and spontaneous process whereby an unstable nucleus loses energy by emitting radiation (e) show an understanding of the nature of alpha (α), beta (β), and gamma (γ) radiation (including ionising effect and penetrating power) [β - particles are assumed to be β– particles only] (f) show an understanding of background radiation (g) use the term half -life in simple calculations, which might involve information in tables or decay curves (h) state the applications (e.g. medical and industrial uses) and hazards of radioactivity.

5105 Science (Physics) Chapter 17 | Radioactivity 2 17.1 What is the composition of an atom? • Subatomic particles: protons, neutrons and electrons • Are held together by: strong attractive forces • Positively charged nucleus and negatively charged electrons. • Nuclide Notation: Example 1 (17A): (a) No. of protons = 92 (b) No. of neutrons = 235 – 92 = 143 Nucleon (mass) number : Total number of neutrons and protons in the nucleus of an atom Proton (atomic) number : Number of protons or Number of electrons in an atom Chemical symbol of the nuclide To find number of neutrons N, N = Nucleon Number A – Proton Number Z in a nucleus Electron : negatively charged Neutron : does not carry any charge. Proton : positively charged -1 +1 0

5105 Science (Physics) Chapter 17 | Radioactivity 3 Example 2 (Let’s Practise 17.1) (d) What is the nuclide notation of the atom? (a) 84 protons (b) 84 electrons (atom is neutral) (c) No. of neutrons = 209 - 84 = 125 (d) 209 X 84 Isotopes Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. • Isotopes of the same element have identical chemical properties. 17.2 What is radioactivity? Nuclear Decay Nuclear decay is a random process by which an unstable atomic nucleus loses its energy by emission of electromagnetic radiation or particle(s) Nuclear decay is also known as radioactive decay or radioactivity. The instability of the atomic nuclei is because the nuclear forces within the nuclei are not enough to bind the