Chapter 2 Atoms and Radioactivity

1. Lecture Presentation Chapter 2Atoms and Radioactivity Julie Klare Fortis College Smyrna, GA

2. Outline • 2.1 Atoms and Their Components • 2.2 Atomic Number and Mass Number • 2.3 Isotopes and Atomic Mass • 2.4 Radioactivity and Radioisotopes • 2.5 Nuclear Equations and Radioactive Decay • 2.6 Radiation Units and Half-Lives • 2.7 Medical Applications for Radioisotopes

4. Dalton’s Atomic Theory 1808 1. Elements are composed of atoms • Atoms are indivisible • Atoms of a given element are identical • Neither created nor destroyed. iClicker Are atoms indivisible? A = true B = false Are atoms of the same element identical? A = true B = false

5. Dalton’s Atomic Theory 1808 3. Compounds are combinations of atoms Water - H2O hydrogen peroxide - H2O2 Carbon dioxide - CO2 carbon monoxide - CO Sodium chloride - NaCl 4. Chemical Reaction = atom rearrangement - Explains Law of conservation of mass.

6. Dalton’s Atomic Theory 1808 1. Elements are composed of atoms • Atoms are indivisible • Atoms of a given element are identical 3. Compounds are combinations of atoms 4. Chemical Reaction = atom rearrangement - Explains Law of conservation of mass. Point # 2 above is technically incorrect (although still useful). In two sentences explain why the 1st two lines (one sentence each) are incorrect.

7. atom – The simplest component of an element that retains its identity. Subatomic particles • Structure of an Atom • Protons and neutrons are clustered together in the nucleus. • Electrons are dispersed throughout the area around the nucleus. • The space occupied by the electrons is called the electron cloud since the electrons are constantly moving and are difficult to pinpoint • Most of an atom consists of empty space.

8. atomic number = # protons mass number = # protons + # neutrons isotope Li 6 7 mass number Li 3 3 atomic number Isotope – relationship between two atoms with the same atomic number, but different mass numbers. (still same element) Lithium – 7 The most common isotope of lithium 7 Li

9. Atomic Number and Mass Number Which is the most abundant isotope of Ca? a) A = 40 b) A = 42 223 7 1 133 39 85 23 Fr Cs Li Rb H Na K 1 3 55 37 19 11 87 List the complete element symbols for the most abundant isotope of each alkali metal. Indicate the # of protons, neutrons, and electrons in each. (3 minutes) 223 Fr 87p, 87e, and 223-87 = 136n 87

10. What is a mole? 1. mole : a pigmented spot, mark, or small permanent protuberance on the human body. 2. mole : any of numerous burrowing insectivores with minute eyes, concealed ears, and soft fur. (one who works in the dark) (a spy)

11. What is a mole? 4. A massive work formed of masonry and large stones or earth laid in the sea as a pier or breakwater. 6. A spicy sauce made with chilies and usually chocolate and served with meat. (molé) 5. The base unit of amount of pure substance in the International System of Units that contains the same number of elementary entities as there are atoms in exactly 12 grams of the isotope carbon-12. 1 mole = the number of C atoms in 12 g of pure carbon-12. 1 mole = 6.022 x 1023 of any item (Avogadro’s Number) A mole is like a dozen (only a lot more)

12. The Atomic Weight (AW) of C is 12.011. • What are the proper units for this? • amu (or atomic mass units) • Grams per mole • Grams • Pounds • Either a or b are correct.

13. Atomic # (Z) = # protons & # electrons Metal vs. nonmetal(metalloid) Period # e 1 2 2 8 3 8 4 18 5 18 6 32 7 32 Main Group elements (6 per period) electrons in p orbitals Main Group elements (2 per period) electrons in s orbitals Transition metals (10 per period) electrons in d orbitals Rare Earth Metals (14 per period) electrons in f orbitals

14. 4 4 0 1 0 0 e e g He a n 0 1 -1 2 2 0

16. How is a nuclear decay equation written? Note there is a conservation of …… mass (mass #) & charge (atomic #) Carbon-14 is a b emitter. Write the equation for its radioactive decay. What element is produced by this decay? a) boron-14 b) carbon-13 c) nitrogen-15 d) nitrogen-14

17. Half-life: The time required for half the amount of a radioactive substance to decay. Half-life: This time is independent of the amount. How long will it take for 1 radioactive 14C atom to decay?

18. 2.7 Medical Applications for Radioisotopes • Certain elements concentrate in particular organs of the body. • If a radioisotope of this element can be made, this area of the body can be imaged using that radioisotope. • A patient can be injected with a trace amount of a radioisotope to diagnose a diseased state. • Radioisotopes can also be used to treat diseases. • Radioisotopes can be applied externally (external beam radiation therapy) or internally (brachytherapy) by applying radiation directly at the tumor site in high doses, eliminating cancerous cells. • Positron emission tomography (PET) uses a radioisotope to image tissues that are not functioning normally.

19. The two main uses of medical radioisotopes are the following: • Diagnosing diseased states • Therapeutically treating diseased tissues • When diagnosing a diseased state, a minimum amount of radioisotope is administered. • The isotope is for detection only and should have minimal effects on body tissue. • A radioisotope used this way is a tracer.

20. It is important to expose patients to the smallest possible dose of radiation for the shortest time period. • Radioisotopes with short half-lives are selected for use in nuclear medicine. • Iodine is used only by the thyroid gland: • Gamma emitters are useful for diagnosis because gamma radiation can easily exit the body. • If tissue is functioning normally, the radioisotope will be evenly distributed throughout the organ. • If there is a nonfunctioning area in the tissue, a “cold” spot is seen. • Unusual activity, like rapidly dividing cancer cells, shows up as a “hot” spot. http://www.youtube.com/watch?v=oSOFxh1JDAo

21. Radioisotopes and Cancer Treatment • In external beam radiation therapy, gamma radiation generated from cobalt-60 is aimed at a tumor, destroying the tissue. • In brachytherapy, small titanium “seeds” containing radioisotopes are implanted in a tumor. K capture 103 103 ? 0 0 + ? Rh g e → Pd + ? 0 45 46 -1

22. Positron Emission Tomography • PET scans are used to identify functional abnormalities in organs and tissues. • Fluorine-18 has a half-life of 110 min. • The fluorine isotope emits a positron as it decays to form oxygen-18. • The positron comes into contact with an electron, and gamma radiation is produced and detected by the scanner. • This type of scan is commonly used for the brain. E.g. a glucose analog with 18F will enter the brain its areas of entry/active use are observed. 18 0 0 0 0 18 e → e + e g + O F → 0 -1 1 1 9 8 If there is a nonfunctioning area in the tissue, a “cold” spot is seen. Unusual activity, like rapidly dividing cancer cells, shows up as a “hot” spot.