1. How many pairs of electrons are shared in a molecule of O 2 ?

1. 1. How many pairs of electrons are shared in a molecule of O2? 2. How many electrons are shared in a molecule of N2?  3. Which formula represents an ionic compound? (1) KCl (2) N2O (3) CCl4 (4) CO2  4. Which formula represents covalent compound? (1) CaCl2 (2) CrCl3 (3) NH3 (4) KBr  5. How many carbon atoms are in the following molecule: C6H12O6  6. How many oxygen atoms are in the following molecule: Ca(NO3)2

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 mg 2 mg 1 mg initial 1 half-life 2 3

3. Examples of Half-Life Isotope Half life C-15 2.4 sec Ra-224 3.6 days Ra-223 12 days I-125 60 days C-14 5700 years U-235 710 000 000 years

4. 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? _______

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?

6. Solution NR3 t1/2 =13 hrs 26 hours = 2 x t1/2 Amount initial = 64mg Amount remaining = 64 mg x ½ x ½ = 16 mg

7. 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?

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

9. Fission

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

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

12. 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

13. Alkane • Hydrocarbon with only single bonds • Compound names end in –ane • CH4 simplest hydrocarbon

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

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

17. CH4 Methane

18. C2H6 Ethane

19. C3H8 • Propane

20. 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

21. Which element is capable of forming stable, extended chains of atoms through single, double, or triple bonds with itself? • A. CarbonB. OxygenC. NitrogenD. Phosphorus

22. The chemical and physical properties of an organic compound are largely determined by the presence of a(n)? • A. IsomerB. AllotropeC. Functional group D. Skeletal structure

23. A hydrocarbon with the formula C8H18 is called? • A. OcteneB. Octane C. OctyneD. Propane

24. 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