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PERIODIC TABLE Periods go across: 1 st period H  He 2 nd period Li  Ne

PERIODIC TABLE Periods go across: 1 st period H  He 2 nd period Li  Ne 3 rd period Na  Ar Groups go down: 1 st group Alkali Metals Li  Fr 2 nd goup Alkaline Earth Metals Be  Ra … Last group Noble/Inert Gases He  Rn.

phillip-larsen
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PERIODIC TABLE Periods go across: 1 st period H  He 2 nd period Li  Ne

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  1. PERIODIC TABLE Periods go across: 1st period H  He 2nd period Li  Ne 3rd period Na  Ar Groups go down: 1st group Alkali Metals Li  Fr 2nd goup Alkaline Earth Metals Be  Ra … Last group Noble/Inert Gases He  Rn

  2. RELATIVE ELECTRONEGATIVITIESUp and to the right: electronegativity increases.(same trend for ionization energy & electron affinity)RELATIVE SIZESDown and to the left: size increases. Smallest size Highest EN IE EA Largest size Lowest EN IE EA

  3. Metallic Character Most elements in the periodic table are metals - metals lose electrons - good thermal and electrical conductors - malleable and lustrous - non-metals gain electrons - gas, liquid, or brittle solid - poor conductors increasing metallic character

  4. OXIDATION STATES • Atoms tend to lose or gain electrons to achieve an inert gas configuration. • Elements to the right (e.g., O, F) are electronegative • gain electrons to become negatively charged (anions). • Elements to the left (e.g., Cs, Sr, Al) are electropositive • lose electrons to become positively charged (cations). • NaCl  Na+Cl • MgO  Mg2+O2 • For main group (s- and p-block) elements: • The highest possible positive oxidation state is equal to the Group Number

  5. AQUEOUS SOLUTIONS • Metals lose electrons to form cations in aqueous solutions (e.g, Ba2+) • Non-metals gain electrons when forming anions in solution (e.g., Br-). • Non-metals can also lose electrons to more electronegative elements, as in oxyanions: • e.g., in SO42-, oxidation states are S6+, O2-

  6. OXIDES • Metal Oxides and Hydroxides are basic • more soluble in acidic solutions. • More electropositive central atom gives off electrons (Na+ OH-) • Non-Metal Oxides and Hydroxides are acidic • more soluble in basic solutions. • More electronegative central atom attracts electrons (HNO3  NO3- + H+) • Metalloid Oxides and Hydroxides are amphoteric • More soluble in both acidic and basic solutions compared to pure water.

  7. 2nd row (Li,Be…F) vs. 3rd, 4th, 5th rows • Period II: • Small atoms • The only valence orbitals are 2s and 2p • No 2d orbitals • Maximum number of bonds = 4. • CF4, NH3. • Small size a greater tendency to form  bonds because there is better sideways overlap of p-orbitals. • Period III: • Bigger size. • Valence orbitals: 3s, 3p, and 3d. • Maximum number of bonds > 4. • SiF4, SiF62-, PCl3, and PCl5. • Bigger size less tendency to form  bonds because there is less overlap of p-orbitals.

  8. 2nd row (Li,Be…F) vs. 3rd, 4th, 5th rows

  9. Hydrogen Properties diatomic gas colorless, odorless tasteless most abundant element in the universe rare in its elemental state on earth (it escapes from the atmosphere). Common Oxidation States 0, +1, -1

  10. Hydrogen - Sources Steam reforming(current method of H2 production)CH4(g) + 2 H2O(g)  CO2(g) + 4 H2(g) (natural gas)Uses Ni catalyst at 800oC Carbon monoxide (CO) is made as a byproduct.water gas shift (converts CO at 300oC using Cu catalyst)CO(g) +H2O(g)  CO2(g) + H2(g) Other methodselectrolysis of water (clean but uses too much energy) 2 H2O(l) 2 H2(g) + O2(g) reactions of active metals (lab scale method) H2SO4(aq) + Fe(s)  H2(g) + FeSO4(aq)steam reforming of carbonC(s) + 2 H2O(g)  CO2(g) + 2 H2(g) high temperature catalytic process, coal is the source of carbon.

  11. Hydrogen Isotopes 1H protium most abundant isotope, nucleus consists of a single proton2H deuterium one neutron and often given the symbol “D”. forms the hydrogen component of heavy water (D2O). 3H tritium radioactive isotope: half-life of 12.3 y, not found in nature.Isotope effectsDeuterium and hydrogen exhibit isotopic differences in their reaction rates and properties. E.g., boiling points of heavy water and conventional water are slightly different allowing them to be separated by fractional distillation.

  12. Hydrogen - Commercial applications Main use of H2 in USHaber-Bosch processN2(g) +3H2(g) 2 NH3(g)synthetic fertilizers: (NH3) can also be further reacted to produce nitrate (–NO3) compounds.Other Uses:Production of methanolCO(g) + 2H2(g) CH3OH(l)Hydrogenation CH2 CH2 CH3 CH3converts double bonds into single bonds: unsaturated compounds like oils into saturated fats.

  13. Hydrogen Compounds Molecular hydrideshydrogen bonded covalently to another element. Examples: HCl, HBr, NH3,CH4, Al2H6…exist as molecules (in gas, liq., solid) acid strength increases from left to rightPH3 < H2S < HClbond strength decreases going down familyH2O < H2S < H2Se < H2Te (least stable)

  14. Ionic Hydrides: hydrogen and an alkali metal such as lithiumExamples: NaH (=Na+H-), CaH2strong bases, strong reducing agents react with water or acids to make H2Molecular Hydrides: hydrogen and a non-metalExamples: NH3, H2O, HClcovalent bondingMetallic hydrideshydrogen and a transition metal. retain their metallic characteristicshydrogen atoms are absorbed into the interstices of the metal atomic lattice.

  15. ACTIVE METALS - GROUPS I AND II Group IGroup II Family Alkali Metals Alkaline Earths Electronic config. ns1 ns2 Oxidation State +1 +2 Melting Point Low Higher Bonding Ionic Ionic (except Be) Oxides, hydroxides Basic Basic (exc. amphoteric Be) Electropositive Most Yes Very Reactive  React with Air, Water

  16. DIAGONAL RELATIONSHIPS In many compounds, Li+ resembles Mg2+ rather than Na+. Examples: Li2CO3 and MgCO3 are virtually insoluble in water, while Na2CO3 is very soluble. Ionic Radii: Li+ 0.60Å Na+ 0.95Å Mg2+ 0.65Å

  17. CHEMICALS FROM NaCl • Na metal is obtained by molten salt electrolysis of a 40:60 mixture of Na/Cl/CaCl2. • This mixture melts at 580°C vs. 800°C for • pure NaCl. • Cathode: 2Na+ + 2e- 2Na (l) • Anode: 2Cl- Cl2(g) + 2e- • 2Na+ + 2Cl- 2Na (l) + Cl2(g)

  18. >20,000,000,000 pounds made anually by electrolysis of aqueous NaCl (chlor-alkali process). • Cathode: 2H2O + 2e- H2(g) + 2OH- • Anode: 2Cl- Cl2(g) + 2e- • 2H2O + 2Cl- H2(g) + Cl2(g) + 2OH- • 2Na+ + 2OH- (=2 NaOH) is left behind. • NaOH dissolves hair and skin (e.g., Drano). • Uses: Soap, Rayon, Cellophane, Paper, Dyes. NaOH (caustic soda).

  19. ALKALINE EARTHS Mg, Ca, Sr, Ba compounds are ionic; hydroxides are basic. Metals are obtained by high temperature electrolysis of their molten chlorides. Mg metal is made in three steps from sea water: 1) Add base to sea water: Mg2+ + 2OH- Mg(OH)2(s) 2) Dissolve in HCl: Mg(OH)2(s) + 2HCl  MgCl2(aq) + 2H2O 3) Electrolysis: MgCl2(l)  Mg(l) + Cl2(g) Principal Uses of Mg: Light structural alloys (lighter than Al or Fe, but strong). Light alloys with Zn, Al, or Mn for aircraft wheels, space vehicles, portable tools, and cameras

  20. Rare element - 0.0005% of the earth’s crust is Be Source: The mineral beryl is Be3Al2Si6O18 has different colors due to trace impurities if light blue-green = aquamarine if deep green = emerald Uses: Nuclear reactor parts – strong but transparent to neutrons X-ray tubes have Be windows Be is strong and relatively light and is transparent to X-rays. Be compounds are covalent Be(OH)2 is amphoteric Similar to Al (diagonal relationship) BERYLLIUM

  21. The twelve most abundant elements in the lithosphere: ElementPercent by weight Oxygen 50 Silicon 26 Aluminum 7.5 Iron 4.7 Calcium 3.4 Sodium 2.6 Potassium 2.4 Magnesium 1.9 Hydrogen 0.9 Titanium 0.6 Chlorine 0.2 Phosphorus 0.1

  22. Fifth most abundant element on earth. CaCO3 Depending on form is limestone, marble, chalk. Bones and teeth are largely CaCO3 and Ca3(PO4)2 Tooth Enamel = Ca10(PO4)6(OH)2 = Hydroxyapatite Cavities: Ca10(PO4)6(OH)2 + 8H+ 10Ca2+ + 6HPO42- + H2O Fluoride replaces OH- with F-. F- is a weaker base, so it reacts less with acid. CaCO3(s) + Heat  CaO(s) + CO2(g) (Lime) Very important industrial chemical (steelmaking, concrete). CALCIUM

  23. CaSO4. (H2O)2 (Gypsum) is used to make cement and plaster wallboard. 2 CaSO4. (H2O)2 + Heat  3H2O + (CaSO4)2. (H2O) (Plaster of Paris) Reverse reaction by adding water. BARIUM Barium is very dense. BaSO4 is a dense, very insoluble material used as an additive to concrete in nuclear reactors. This makes the walls more dense. This also makes the walls absorb neutrons. BaSO4 also absorbs X-rays - used by radiologists for stomach X-rays. CALCIUM (cont’d)

  24. WATER SOFTENING Hard water contains dissolved Ca2+ and Mg2+. These form precipitates with soap – bath tub rings. Most detergents do not work well to remove this. Also forms deposits in water pipes. Ca2+(aq) + 2HCO3-(aq)  CaCO3(s) + CO2(g) + H2O from dissolved CO2 scale Scale forms on the bottom of teapots, in faucets, on the walls of hot water pipes and boilers, etc. Can be removed with acid (e.g., vinegar)

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