1. CHP 5.3 REPRESENTATIVE GROUPS PG. 139-145

2. Valence Electrons The “A” groups in the periodic table have numbers that match the number of valence electrons in an electron configuration for an element in that group Valence electron - an electron that is in the highest occupied energy level of an atom. The “A” groups in the periodic table have numbers that match the number of valence electrons in an electron configuration for an element in that group Valence electron - an electron that is in the highest occupied energy level of an atom.

3. Valence Electrons These electrons play a key role in chemical reactions Elements in a group have similar properties because they have the same number of valence electrons Properties vary across a period (row) because the number of valence electrons increases from left to right These electrons play a key role in chemical reactions Elements in a group have similar properties because they have the same number of valence electrons Properties vary across a period (row) because the number of valence electrons increases from left to right

4. Alkali Metals Group 1A elements are called alkali metals They have a single valence electron and are extremely reactive These are found in nature only as compounds The reactivity of alkali metals increases from the top of Group 1A to the bottom

5. Alkali metals Table salt is a compound of sodium and chlorine Sodium is a soft metal that can be cut with a knife. It melts at about 98 0 C and has a lower density than water It reacts violently with water like other elements in this group Sodium and potassium are stored under oil to keep them from reacting with the oxygen and water vapor in air. Table salt is a compound of sodium and chlorine Sodium is a soft metal that can be cut with a knife. It melts at about 98 0 C and has a lower density than water It reacts violently with water like other elements in this group Sodium and potassium are stored under oil to keep them from reacting with the oxygen and water vapor in air.

6. Alkaline Earth Metals Group 2A elements all have 2 valence electrons Harder then metals in group 1A Differences in reactivity among the alkaline earth metals are shown by the ways they react with water

7. Magnesium Helps plants produce sugar A mixture of magnesium and other metals can be as strong as steel but much lighter Frames of bicycles and backpacks often contain magnesium

8. Calcium Helps keep your bones and teeth strong Calcium carbonate (compound of calcium, carbon, and oxygen) is the main ingredient in chalk, limestone, coral and pearl Helps keep your bones and teeth strong Calcium carbonate (compound of calcium, carbon, and oxygen) is the main ingredient in chalk, limestone, coral and pearl

9. The Boron Family (Group 3A) Group 3A contains Boron, Aluminum, Gallium, Indium, and Thallium Aluminum is the most abundant metal in Earth’s Crust and is often found combined with oxygen in a mineral called bauxite Aluminum is strong, lightweight, malleable, and a good conductor of electric current

10. The Carbon Family (Group 4A) Contains Carbon (non- metal), silicon and germanium (metalloids), and tin and lead (metals) Each has 4 valence electrons More metallic as you go down the group Life on earth would not exist without carbon. Except for water, most of the compounds in your body contain carbon. Contains Carbon (non- metal), silicon and germanium (metalloids), and tin and lead (metals) Each has 4 valence electrons More metallic as you go down the group Life on earth would not exist without carbon. Except for water, most of the compounds in your body contain carbon.

11. The Nitrogen Family (Group 5A) Nitrogen and Phosphorus (nonmetals), Arsenic and Antimony (metalloids), Bismuth (metal) Nitrogen and Phosphorus are often found in fertilizers and your body uses compounds containing nitrogen and phosphorus to control reactions and release energy from food Nitrogen and Phosphorus (nonmetals), Arsenic and Antimony (metalloids), Bismuth (metal) Nitrogen and Phosphorus are often found in fertilizers and your body uses compounds containing nitrogen and phosphorus to control reactions and release energy from food

12. The Oxygen Family (Group 6A) Oxygen, Sulfur, and Selenium (nonmetals) Tellurium and Polonium (metalloids) All have 6 valence electrons Oxygen is the most abundant element in Earth’s crust Complex forms of life need oxygen to stay alive because oxygen is used to release the energy stored in food

13. The Halogens (Group 7A) Flourine and Chlorine (gases), Bromine (liquid), Iodine (solid), Astatine (very rare) Despite their physical differences, the halogens have similar chemical properties They are highly reactive nonmetals and flourine is the most reactive Flourine and Chlorine (gases), Bromine (liquid), Iodine (solid), Astatine (very rare) Despite their physical differences, the halogens have similar chemical properties They are highly reactive nonmetals and flourine is the most reactive

14. The Noble Gases (Group 8A) Helium only has two valence electrons but the rest have 8 The noble gases are colorless and odorless and extremely unreactive Hard to discover these elements because they were colorless and odorless An element that does not react easily with other elements can be very useful because it can be used to prevent reactions with highly reactive elements like oxygen