2. 1. How many pairs of electrons are shared in a molecule of O 2 ? 2. How many electrons are shared in a molecule of N 2 ? 3. Which formula represents an ionic compound? (1) KCl(2) N 2 O(3) CCl 4 (4) CO 2 4. Which formula represents covalent compound? (1) CaCl 2 (2) CrCl 3 (3) NH 3 (4) KBr 5. How many carbon atoms are in the following molecule: C 6 H 12 O 6 6. How many oxygen atoms are in the following molecule: Ca(NO 3 ) 2

3. 2 Half-Life of a Radioisotope The time for the radiation level to fall (decay) to one-half its initial value decay curve 8 mg 4 mg2 mg 1 mg initial 1 half-life 2 3

4. 3 Examples of Half-Life Isotope Half life C-152.4 sec Ra-2243.6 days Ra-22312 days I-12560 days C-145700 years U-235710 000 000 years

5. 1. How long is a half-life for carbon- 14?_____________ 2. If only 25% of the carbon- 14 remains, how old is the material containing the carbon-14?________ 3. If a sample originally had 120 atoms of carbon-14, how many atoms will remain after 16,110 years? _______

6. 5 Learning Check NR3 The half life of I-123 is 13 hr. How much of a 64 mg sample of I-123 is left after 26 hours?

7. 6 Solution NR3 t 1/2 =13 hrs 26 hours = 2 x t 1/2 Amount initial =64mg Amount remaining = 64 mg x ½ x ½ = 16 mg

8. After 42 days a 2.0 g sample of phosphorus-32 contains only 0.25 g of the isotope. What is the half-life of phosphorus-32?

9. 8 Nuclear Fission large nuclei break up Nuclei bombarded with neutrons 235 U + 1 n 139 Ba + 94 Kr + 3 1 n + 92 0 56 36 0 Energy

10. 9 Fission

11. 10 Nuclear Fusion Fusion small nuclei combine 2 H + 3 H 4 He + 1 n + 1 1 2 0 Occurs in the sun and other stars Energy

12. 11 Learning Check NR4 Indicate if each of the following are (1)Fission(2) fusion A.Nucleus splits B.Large amounts of energy released C.Small nuclei form larger nuclei D.Hydrogen nuclei react Energy

13. ORGANIC CHEMISTRY Carbom: capable of forming stable, extended chains of atoms through single, double, or triple bonds with itself Hydrocarbons- contain hydrogen and carbon Carbon- 4 bonds Hydrogen- 1 bond

14. Alkane Hydrocarbon with only single bonds Compound names end in –ane CH 4  simplest hydrocarbon

16. Mnemonic for First Four Prefixes First four prefixes Meth- Eth- Prop- But- Monkeys Eat Peeled Bananas

17. ? Decade Decimal Decathalon Other Prefixes Pent- Oct- Dec- Hex-, Hept-, Non-

18. CH 4 Methane

19. C2H6C2H6 Ethane

20. C3H8C3H8 Propane

21. Functional Groups Specific arrangement of atoms in an organic compound that largely determines the chemical and physical properties of the organic compound Organic compounds classified according to their functional groups Examples on Page 799

22. Which element is capable of forming stable, extended chains of atoms through single, double, or triple bonds with itself? A. Carbon B. Oxygen C. Nitrogen D. Phosphorus

23. The chemical and physical properties of an organic compound are largely determined by the presence of a(n)? A. Isomer B. Allotrope C. Functional group D. Skeletal structure

24. A hydrocarbon with the formula C 8 H 18 is called? A. Octene B. Octane C. Octyne D. Propane

25. Chromium-48 has a short half-life of 21.6 h. How long will it take 360.00 g of chromium-48 to decay to 11.25 g