the elements representative and transition elements section 15-1 and 15-2

The Elements

Representative and Transition ElementsSection 15-1 and 15-2

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Groups 1 and 2

• Always found in nature combined with other elements

• Active metals– Readiness to form new substances

• All metals except hydrogen

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Alkali Metals

• Silvery solids

• Low densities

• Low melting points

• Increase in reactivity as you move from top to bottom– Most reactive is Francium

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Alkali Metals

• Uses:– Lithium—batteries– Sodium—table salt– Sodium and Potassium—dietary

requirements

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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

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Alkali Earth Metals

• Uses:– Beryllium—found in gems emerald

and aquamarine– Magnesium—found in chlorophyll

of green plants

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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

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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

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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

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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

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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

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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

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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

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Transition Elements

• Groups 3-12

• All metals

• Most found combined with other elements in ores

• Few found as pure elements (gold and silver)

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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

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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

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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

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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

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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