Teacher Notes: Ch 17 Nuclear Chemistry

1. Teacher Notes:Ch 17Nuclear Chemistry

2. Ch 17.1-17.2Topic:RadioactivityEQ: How was radioactivity discovered and what is it?

3. Ch 17.1 • Some isotope’s are not stable. • The emitted subatomic particles are called nuclear radiation. • The isotopes that emit them are termed radioactive. • Nuclear radiation can be harmful - damage biological molecules. • But not all Radioactive isotopes are harmful.

4. Ch 17.2: The Discovery of Radioactivity • In 1895 William Roentgen discovered X-rays, a form of radiation.

5. Ch 17.2: The Discovery of Radioactivity • In 1896, French scientist Antoine-Henri Becquerel (1852–1908), discovered radioactivity. • He studied Uranium minerals that emit light after being exposed to sunlight, a phenomenon called phosphorescence.

6. Ch 17.2 The Discovery of Radioactivity • Marie Curie (1867–1934), one of the first women in France to attempt doctoral work by studying uranic rays for her doctoral thesis. • Her first task was to determine whether any other substances besides uranium emitted rays. • In 1898, Marie Curie and her husband Pierre (1859–1906) took Becquerel’s mineral sample (called pitchblende) and isolated the components emitting the rays.

7. The Discovery of Radioactivity: Marie Curie • In 1903, Curie received the Nobel Prize in physics for the discovery of radioactivity. • Curie discovered two new elements. Curie named one of her newly discovered elements polonium after her home country of Poland.

8. Curie named the 2nd element Radiumbecause of the very high amount of radioactivity that it produced. • Radium was so radioactive that it glowed in the dark and emitted significant amounts of heat. • In the past, radium was added to some paints (watch dials that made the dial glow)

9. The Discovery of Radioactivity • In 1911, Curie was awarded a second Nobel Prize, this time in chemistry, for her discovery of the two new elements polonium and radium. • She is the first woman to win the Nobel Prize and is the only person to receive Nobel Prizes in two different sciences – physics and chemistry!!! • Element 96 (curium) is named in honor and her contributions to our understanding of radioactivity.

10. An Unstable System • The rays and particles emitted by a radioactive source are called radiation. • REMEMBER…..Isotopes are atoms of the same element that have different numbers of neutrons and mass number. • Isotopes of atoms with unstable nucleus are called radioisotopes.

11. Nuclear Reactions vs. Chemical Reactions(3 differences - Muy Importante!!!) 1. Marie Curie discovered that chemical Reactions were affected by Pressure and Temperature, whereas nuclear reactions were not affected by P and T. 2. Chemical Reactions involve electrons, not protons and neutrons. 3. Nuclear reactions involve the nucleus;changes protons & neutrons . • THIS CHANGES THE IDENTITY OF ELEMENT!!!!

12. Ch 17.3-17.4Topic: Types of RadiationsEQ: What are the different types of radioactive decay?

13. Ch 17.3: Main Types of Radiation • Five Types: • Alpha (α) • Beta (β) • Gamma (γ) • Positron • Electron Capture

14. Draw with notes Radioactivity is the emission of tiny, energetic particles by the nuclei of certain unstable atoms. Nuclei are unstable when they are too large or contain an unbalanced ratio of neutrons to protons. Radioactivity

15. Isotope Notation Any isotope can be represented with the following notation: The main subatomic particles—protons, neutrons, and electrons—can be represented with similar notation. • FYI - Proton – usually referred to as hydrogen

16. Types of Radiation 0 −1 0 −1 e  or • Alpha (ά) – a positively charged helium isotope • Beta (β) – an electron • Gamma ray (γ) – pure energy

17. Other Nuclear Particles 0 +1 0 +1 0 −1 e e  or • Positron – a positive electron • Electron capture

18. Nuclear Equations • A nuclear equation represents the changes that occur during radioactivity. • Example: • The term nuclideis used in nuclear chemistry to mean a specific isotope. • The original atom is called the parent nuclide, and the products are called the daughter nuclides.

19. Nuclear Equations Must Be Balanced • Check your work….. The sum of the atomic numbers on both sides of a nuclear equation must be equal, and the sum of the mass numbers on both sides must also be equal.

20. Penetrating Power • Penetrating power is the ability to penetrate matter. In order for radiation to damage important molecules within living cells, it must penetrate the cell.

21. Alpha Radiation Alpha (α) Radiation occurs when an unstable nucleus emits an αparticle composed of 2 protons and 2 neutrons.

22. Alpha Radiation (α) • helium nucleus • charge is 2+ Mass # charge

23. Alpha radiation: most massive of all particles. • Has the lowest penetrating power • Alpha radiation - can be stopped by a sheet of paper, by clothing, or even by air.

24. 210 84 210 84 Po Po + + + + + + + + LEFT side Alpha Decay a Particle +

25. LEFT side Writing Nuclear Equations • Alpha Decay of Th – 232….

26. Alpha Decay 238 92 4 2 U He +  LEFT side Types of Radioactive Decay

27. Alpha Decay 239 94 234 92 Pu U + +   LEFT side Types of Radioactive Decay

28. Beta radiation occurs when an unstable nucleus emits an electron.

29. 0 −1  Beta Radiation • A Beta particle is a very-fast moving electron Mass # Charge

30. Beta radiation: • much less massive than alpha particles • have greater penetrating power • a sheet of metal (like foil) or a thick piece of wood is required to stop them.

31. 14 6 14 6 - C C + + + + + + + + + + + + + LEFT side Beta Decay b Particle + - +

32. 131 53 0 −1 I e +  LEFT side Types of Radioactive Decay Beta Decay

33. Beta Decay 25 11 6 2 He Na + +   LEFT side

34. Gamma (γ) Radiation • Different from alpha or beta radiation. • Gamma radiation is not matter but electromagnetic radiation. • Gamma rays are high-energy (short-wavelength) photons (bundles of light). • A gamma ray has no charge and no mass.

35. Gamma (γ) Ray Radiation Damage Potential • Gamma rays: • Highestpenetrating power. • Stopping gamma rays requires several inches of lead shielding or thick slabs of concrete.

36. Radiation Draw LEFT side

37. Penetrating Ability

38. Positron emission occurs when an unstable nucleus emits a positron (positive electron).

39. The symbol for a positron is: • Positron - same mass as an electron but opposite charge. • Positron emission is similar to beta emission in its penetrating power.

40. 11 6 0 1 C e +  LEFT side Types of Radioactive Decay Positron Emission

41. Positron emission and electron capture • Electron captureoccurs when the nucleus of an atom draws in a surrounding electron. • Written on left side of rxn!!

42. Table 17.1 Selected Types of Radioactive Decay Draw LEFT side – Great Summary of radiations

43. LEFT side Balancing a Nuclear Equation • Write a balanced nuclear equation for the alpha decay of gold-230.

44. LEFT side Question 2 What element is formed when silver - 110 radioisotope undergoes alpha decay?

45. What element is formed when undergoes a. beta decay? b.Positron decay? LEFT side Question 3

46. What element is formed when undergoes a. neutron decay? b.electron capture decay? LEFT side Question 4

47. LEFT side Checking for Understanding

48. Ch 17.5Topic: Detecting Radiations and Half lifeEQ: How is radiation detected?

49. Detecting Radioactivity • Film-badge dosimeters consist of photographic film held in a small case that is pinned to clothing. • The badges are collected and processed as a way to monitor exposure to radiation. • The more exposed the film has become, the more radioactivity to which the person has been exposed.

50. Geiger-Müller Counter • Energetic particles emitted by radioactive nuclei pass through a chamber filled with argon gas and ionize (create ions) it. • Creating a tiny electrical current between the + and - charges. • This electrical signal can be detected on a meter. • The “Clicking” is the sound most people associate with a radiation detector.