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Periodic Properties: Groups 5A, 6A, and 7A Group 5A Elements and Symbols Element Type State

Periodic Properties: Groups 5A, 6A, and 7A Group 5A Elements and Symbols Element Type State N = Nitrogen Non-metal diatomic gas P = Phosphorous Non-metal solid As = Arsenic Metalloid solid Sb = Antimony Metalloid solid Bi = Bismuth Metal solid

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Periodic Properties: Groups 5A, 6A, and 7A Group 5A Elements and Symbols Element Type State

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  1. Periodic Properties: Groups 5A, 6A, and 7A • Group 5A • Elements and Symbols Element Type State • N = Nitrogen Non-metal diatomic gas • P = Phosphorous Non-metal solid • As = Arsenic Metalloid solid • Sb = Antimony Metalloid solid • Bi = Bismuth Metal solid • Some chemistry of the non-metal Group 5A Elements • The elements tend to react to gain 3 electrons to be like noble gas • These elements react with oxygen to form acidic compounds • HNO3 = Nitric Acid H3PO4 = Phosphoric Acid • P4(s) + 5 O2(g) -----> P4O10(s) • P4O10(s) + 6 H2O -----> 4 H3PO4(aq) • c. Important Biological Elements • N is a component of every amino acid (protein) and DNA • P is a component of DNA

  2. d. Phosphorous has more than one allotrope • Allotrope = stable solid phase • P4(s) is called “white phosphorous” is tetrahedral, and burns in air • Pred is called “red phosphorous” and is made of chains of P4 tetrahedra • Pblack is called “black phosphorous” and is a crystalline solid • We will be reacting Red Phosphorous with Oxygen today in lab • Don’t bother with the bottle • Burn the phosphorous in the bunsen burner in the hood • Have a distilled water dampened piece of pH paper ready • Put the pH paper (green when damp) in the phosphorous smoke • If it turns red, that indicates the formation of acid • DON’T PUT HOT COMBUSTION SPOON INTO BOTTLE!!!

  3. Group 6A • 1. Elements and Symbols Element Type State • O = Oxygen Non-metal diatomic gas • S = Sulfur Non-metal solid • Se = Selenium Non-metal solid • Te = Tellurium Metalloid solid • Po = Polonium Metalloid solid • 2. Some chemistry of the non-metal Group 5A Elements • The elements tend to react to gain 2 electrons to be like noble gas • 20% of the atmosphere and 50% of the crust is O (by mass) • These elements react with oxygen to form acidic compounds • Sulfuric Acid (H2SO4) is the largest volume chemical used in industry • - S(s) + O2(g) -----> SO2(g) • SO2(g) + H2O(l) -----> H2SO3(aq) = sulfurous acid • We will be burning S(s) in the hood to produce H2SO3 • Use same procedure as for phosphorous • All waste P and S should be completely burned off of the spoon

  4. Sulfur has more than one Allotrope • Two allotropes of solid sulfur have 8-membered rings, but different crystal forms: “monoclinic” and “rhombic” • If liquid sulfur is cooled quickly, it solidifies as chains of sulfur atoms called “plastic sulfur” rhombic plastic monoclinic

  5. Sodium Reacts Violently with Chlorine • Group 7A = Halogens (kJ/mol) • 1. Elements Element Type State E.A. • F = Fluorine Non-metal diatomic gas, yellow -328 • Cl = Chlorine Non-metal diatomic gas, yellow -349 • Br = Bromine Non-metal diatomic liquid, brown -325 • I = Iodine Non-metal diatomic solid, purple -295 • At = Astatine Non-metal radioactive solid • The chemistry of these elements is dominated by their need to add one e- • 2 Na(s) + Cl2(g) -----> 2 NaCl(s) + large amount of heat

  6. 3. Electron Affinity = energy given off when a gaseous element gains an e- • X(g) + e- -----> X-(g) • Exothermic process because all elements accept e- due to + nucleus • Adding e- is less favored down a group due to distance from nucleus • Fluorine is so small, that repulsion from other electrons lowers its E.A. • Halogens with more favorable E.A. can take electrons from other halides • Cl2 + 2 Br- -----> 2 Cl- + Br2 • E.A: -349 -325 • Cl2 is reduced; Br- is oxidized • We will be studying this kind of reaction today in lab • Prepare control samples: • I2/H2O + toluene = purple color of I2 in toluene • Br2/H2O + toluene = orange color of Br2 in toluene • Cl2/H2O + toluene = yellow color of Cl2 in toluene I2 Cl2 Br2

  7. Run all possible combinations of reactions between Cl/Br/I and observe the color of the toluene when finished • Cl2 + Br- -----> yellow (Cl2) if no reaction; orange (Br2) if reaction • Cl2 + I- -----> • Br2 + Cl- -----> • Br2 + I- -----> orange (Br2) if no reaction; purple (I2) if reaction • I2 + Cl- -----> • I2 + Br- -----> • Use parafilm to cover test tubes to shake them up • All halogen reactions go into a waste beaker in the hood

  8. Incident: HF and Trifluoroacetic Acid Burn • Incident: HF Exposure

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