1. 4.2 Representative Elements I. Groups 1 and 2 A. Alkali Metals (Group 1) 1. Silvery solids 2. Low densities and low melting points 3. Highly reactive 4. Increasing reactivity from top to bottom on table B. Alkaline Earth Metals (Group 2) 1. Harder and denser than Group 1 neighbor 2. Not as reactive as Group 1 neighbors

2. II. Groups 13 through 18 A. Group 13 – The Boron Family 1. All metals except Boron 2. Variety of uses B. Group 14 – The Carbon Group 1. All three states of matter 2. Silicone: used in semiconductors 3. Carbon found in ALL living things. C. Group 15 – The Nitrogen Group 1. Nitrogen and phosphorous used in fertilizers 2. Phosphorous used in explosives

3. D. Group 16 – The Oxygen Family 1. Oxygen: required for life and combustion 2. Selenium: conducts electricity in light E. Group 17 – The Halogen Group 1. All non-metals EXCEPT astatine (metalloid) 2. Halogen = “salt former” 3. Decreasing reactivity top to bottom F. Group 18 – The Noble Gases 1. Rarely combine with other elements 2. Found this way in nature G. Uses for Noble Gases 1. “Neon” lights: each gas glows a different color.

4. 2. Krypton: landing lights at airports 3. Xenon: flashbulbs 4. Radon: found in rocks; causes lung cancer