UU chem ch 6B notes element families
Chemistry of group 1A elements: Alkali metals
Valence shell ns1, smallest ionization energies, +1 ions, reducing agents (donate electron), metallic, soft, low melting points and densities, stored in oil for reacts with oxygen and moisture, none found in elemental state in nature but as salts.
Uses of alkali metals
Lithium- found 1817, lithos means stone - found in rocks, automotive greases, Li2CO3 – treatment of bipolar disorder
Sodium - 1807, from caustic soda (NaOH), table salt (NaCl), found in oceans and seas
Potassium – 1807, from potash (K2CO3),from left over wood fires, plant fertilizer
Rubium, Cesium – colored impurities in rock and named for (Red –rubidius and Caesius - Sky Blue)
Francium – highly radioactive, no visible amounts made
Chemistry of group 2A elements: alkaline earth metals
Valence shell ns2, reducing agent, lose 2 electrons, +2 charge, soft but harder than alkali, low but higher than alkali melting points and densities, less reactive, found only as salts
Uses of alkaline earth
Beryllium – 1798, in gemstone beryl, toxic if inhaled, form hard - corrosive resistant alloy.
Magnesium – 1808, Named for area found, talc, dolomite, sea water, alloy with Al- engines
Calcium – 1808, CaCO3 – ancient sea beds, bones named calx -Lime, marble, chalk, coral, cement
Strontium, Barium – Sr – 1787, Strontian Scotland, SrCO3 – glass for T.V., Ba- (barite) BaSO4 – drink for digestive X rays.
Radium – 1898, Curie found with U, was used in cancer radiotherapy
Chemistry of the Group 3A elements: Aluminum
1st of p block elements, ns2 np1, most metals (one nonmetal), lose 3 electrons for +3 oxidation number,
Hall - Heroult process to remove aluminum form its ore.
Uses of group 3
Boron – metalloid, borax – cleansing , boric acid in eye wash
Aluminum – most abundant in earth’s crust, alum (medicine salt in Roman times), Al2O3 gems with (Cr – ruby, Fe / Ti – sapphire), made from bauxite by passing current, self protect metal with oxide forming on surface
Gallium – low melting point 29.8, in hand
Group 4
Variety of properties from nonmetal to metal, ns2 np2, tin and lead +4 charge, other share forming covalent compounds.
Uses of group 4
Silicon – sand (SiO2), making ceramics / glass and computer chips, lubricants / sealants
Tin – protective coating for steel cans, alloys: bronze, solder, pewter, Tin foil
Lead – from galena (PbS), alloy: solder, cheap pewter, lead acid storage batteries in cars, lead poisoning – decreased mental functions
Group 5
Valence shell of ns2 np3, need 3 electron to fill valence shell so gain 3 electrons for a -3 oxidation number, nonmetal (N, P) to metalloid (As, Sb) to metal (Bi), (can have +3, +5)
Uses of group 5
Nitrogen – proteins, DNA, RNA, 78% of air – not usable so bacteria on legumes it to ammonia (NH4+) (fertilizer) and nitrate, lightning (NO)
Phosphorus – Phosphate group (PO4-3), ATP, red in matches
Arsenic – with Ga for electronics
Antimony – improves hardness and corrosion resistance in alloys.
Group 6
Valence shell ns2 np4, need 2 electrons to fill shell so gains 2 electrons, +2 charge
O, S, Se, Te (nonmetals) Po (metalloid)
Since most nonmetals form covalent bonds
Uses of group 6
Oxygen – most abundant element, 21% atmosphere, water, ozone (O3)– pollutant lower “smog” protect from UV in upper atmosphere. Hydrogen peroxide (H2O2),
Sulfur – Frasch process, sulfuric acid – batteries, rubber
Selenium – security and mechanical devices, photocopier
Chemistry of the Group 7A Elements: Halogens
Valence shell ns2 np5, need 1 electron to fill shell so gains 1 electron for a -1 oxidation charge, very reactive and not found free, diatomic – bound to itself
Halogen – means salt (hals) former (gennax)
Uses of group 7
Fluorine – pale-yellow gas, most reactive, toothpaste (NaF), Teflon (C2F4)n
Chlorine-1774 , greenish – yellow gas, kills bacteria in water, bleach, PVC pipes
Bromine – 1826, reddish liquid, photographic film (AgBr2)– light sensitive coating on film.
Iodine – 1811 from sea weed ash, purple liquid, antibacterial, thyroid gland uses it
Astatine – radioactive, minute (< 1g) in nature
Chemistry of the group 8A elements: Noble gases
Full valence shell ns2 np6, colorless, odorless, unreactive /inert gases. 1s2 for Helium.
Uses for group 8
He- used in balloons because “lighter than air” and less reactive than Hydrogen, 2nd most abundant in universe (star fusion – H 75%)
Neon – gas pass current through glows red
Krypton and Xenon have F compounds
Argon – 1% of atomosphere, lightbulbs
Radon – low-level cancer risk, produced by radioactive decay of Radium
Trends in properties of transitional elements
Have high melting point and boiling point (except zinc column); increases from Group 3 to maximum group 5/6 and decrease across the remainder. Tungsten – highest metal, Mercury – lowest, liquid at room temperature
Have many oxidation state due to involvement of the d electrons (close energy to s orbital) in chemical bond (only heavy main group display this property)
Trends in atomic size of transitional elements
Similar trend to main group, just not as dramatic.
Atomic radii increase as go down the group
Atomic radii decreases at you go down a period.
Iron
Needed in biology – Hemoglobin
Magnetic
Separated from Ore (oxides) in blast furnace, to produce pig iron where slag is drawn off.
Iron with additives (carbon or transitional) to give steel with different properties. Surgical steel is hardest.
Heat treating – iron reacts with carbon to form a carbide that dissolves in steel.
Damascus steel
Other transitional elements
Iron triad – Fe, Co, Ni
Platinum group – Ru, Rh, Pd, Os, Ir, Pt: used as catalyst to speed up reactions
Coinage metals- Cu, Ag, Au: used for coins because malleable, less reactive, rare
Chromium – Corrosion – resistance, self protecting, variety of colored compounds
Zinc – corrosion – resistance, galvanize –surface coating of steel, Brass when add Cu.
Inner transitional elements
Little change in atomic size in period 5 and 6 so they have similar properties
Cerium – misch metal alloy, flint for lighters, glass polish
Neodymium – welder’s shield
Some in control rods – nuclear (absorb neutrons)
electronics
Actinides
Uranium – radioactive element for nuclear fuel
Plutonium – nuclear fuel, power source in pacemakers and buoys.