The Elements Representative and Transition Elements Section 15-1 and 15-2

Groups 1 and 2 Always found in nature combined with other elements Active metals –Readiness to form new substances All metals except hydrogen

Alkali Metals Silvery solids Low densities Low melting points Increase in reactivity as you move from top to bottom –Most reactive is Francium

Alkali Metals Uses: –Lithium—batteries –Sodium—table salt –Sodium and Potassium—dietary requirements

Alkali Earth Metals Each is denser, harder, and has a higher melting point than the alkali metal in same period Reactive, but not as reactive as alkali metals

Alkali Earth Metals Uses: –Beryllium—found in gems emerald and aquamarine –Magnesium—found in chlorophyll of green plants

Groups 13 thru 18 Not all solid metals A single group can contain metals, nonmetals, and metalloids A single group can also have members that are solids, liquids, and gases

Group 13—Boron Family All metals except boron (brittle, black metalloid) Used to make a variety of products –Cookware—boron –Soft-drink cans—aluminum –Computer chips--gallium

Group 14—Carbon Group Carbon—nonmetal –Diamond and graphite –Found in all living things Silicon & Germanium—metalloid –Semiconductors –Computer chips Tin & Lead –Two heaviest elements in group –Lead—x-ray aprons, car batteries –Tin—pewter, toothpaste, coating for steel cans

Group 15—The Nitrogen Group Nitrogen & Phosphorus –Nonmetals –Required by living things –Part of DNA Nitrogen –80% of air you breathe –Get nitrogen for body from eating plants Phosphorus –White phosphorus—can’t be exposed to air—it will explode !! –Red phosphorus—used for head of matches –Also needed for healthy teeth and bones

Group 16—the Oxygen Family Oxygen –20% of Earth’s atmosphere –Required for combustion –Ozone shields organisms from radiation Sulfur –Solid, yellow nonmetal –Used to make sulfuric acid Paint, fertilizer, detergent, rubber Selenium –Conducts electricity when exposed to light –Used in solar cells, photographic materials

Group 17—The Halogen Group All metals except for astatine (radioactive metalloid) Means “salt-former” –Example, table salt—sodium chloride Most reactive is fluorine Least reactive is iodine

Group 18—The Noble Gases Rarely combine with other elements Great for signs –Each glows a different color light when electricity is passed through Helium –Less dense than air –Great for balloons Argon –Most abundant Krypton –Used to illuminate landing strips Radon –Radioactive; produced naturally –Harmful; can cause lung cancer

Transition Elements Groups 3-12 All metals Most found combined with other elements in ores Few found as pure elements (gold and silver)

Iron Triad Elements in period 4 –Iron, cobalt, nickel Have magnetic properties Industrial magnets—alloy of nickel, cobalt, aluminum Nickel used in batteries Iron is necessary in hemoglobin to transport oxygen in body Iron also combined with other metals to produce steel

Uses of Transition Elements Tungsten—highest melting point of any metal –Used as filament in light bulbs Mercury—lowest melting point –Used in thermometers and barometers –Only metal liquid at room temperature –Poisonous to living things

Uses of Transition Elements Chromium—comes from Greek word for color, chroma –Used in paints Platinum group –Ruthenium, rhodium, palladium, osmium, iridium, and platinum –Can be used as catalysts –Used to produce electronics

Lanthanides Also called rare earth elements Usually found in combination with oxygen in Earth’s crust Soft metals than can be cut with a knife

Actinides All radioactive Thorium, protactinium, uranium are only ones found naturally on Earth Plutonium—used to fuel nuclear power plants Americium—used in smoke detectors Californium-252—used to kill cancer cells