REPRESENTATIVE GROUPS (5.3)

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

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

Alkali Metals (1A) Have a single valence electron Extremely reactive Found in nature only as compounds The reactivity increases from the top of group to the bottom

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 980 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

Alkaline Earth Metals (2A) Have 2 valence electrons Harder than metals in 1A Differences in reactivity among the alkaline earth metals are shown by the ways they react with water

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

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

The Boron Family (3A) 3 valence electrons 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

The Carbon Family (4A) Contains Carbon (non-metal), silicon and germanium (metalloids), and tin and lead (metals) 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

The Nitrogen Family (5A) 5 valence electrons 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

The Oxygen Family (6A) Oxygen, Sulfur, and Selenium (nonmetals) Tellurium and Polonium (metalloids) 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

The Halogens (7A) 7 valence electrons 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

The Noble Gases (8A) Helium only has two valence electrons but the rest have 8 Are colorless, odorless and extremely unreactive Hard to discover these elements because they were colorless and odorless Does not react easily with other elements and can be used to prevent reactions with highly reactive elements like oxygen