The Representative Elements: Group 5A Through 8A.

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The Representative Elements: Group 5A

Through 8A

Properties of Nitrogen

Atomic Number 7

Density (g/L) 1.25

Melting Point (oC) -210

Boiling Point (oC) -196

Atomic Radius (pm) 74

Ionic Radius, N-3 (pm) 171

Electronegativity 3.0

How Air Bags Work

In an accident, sensors initiate the reaction with a spark

2NaN3(s) => 2Na(s) + 3N2(g)

reactive sodium destroyed by

10Na(s) + 2KNO3(s) => K2O(s) + 5Na2O(s) + N2(s)

heat converts hazardous products into glass

K2O(s) + Na2O(s) + SiO2(s) => glassheat

Ostwald Process: Nitric Acid

4 NH3(g) + 5 O2(g) => 4 NO(g) + 6 H2O(g)

2 NO(g) + O2(g) => 2 NO2(g)

3 NO2(g) + H2O(l) => 2 HNO3(aq) + NO(g)

Nitrogen Cycle

Properties of Phosphorus

Atomic Number 15

Density (g/L) 1.82

Melting Point (oC) 44

Boiling Point (oC) 280

Ionic Radius, P-1 (pm) 212

Phosphate Fertilizers

2Ca3(PO4)2 +6SiO2 +10C (1500°C) 6CaSiO3

+ 10CO + P4

The reaction may proceed via "phosphorus pentoxide", P4O10

2Ca3(PO4)2 + 6SiO2 6CaSiO3 + P4O10

P4O10 + 10C 10CO + P4

Isolation of P

•used in the manufacture of safety matches, pyrotechnics, incendiary shells, smoke bombs, tracer bullets, etc. •Fertilisers(肥料 )•phosphates are used in the production of special glasses, such as those used for sodium lamps •bone-ash, calcium phosphate, is used to produce fine chinaware and to produce monocalcium phosphate used in baking powder •important in the production of steels, phosphor bronze, and many other products •Na3PO4 is important as a cleaning agent, as a water softener, and for

preventing boiler scale and corrosion of pipes and boiler tubes •pesticides (殺蟲劑 )

磷循環

FeAsS (700°C) FeS + As(g) As(s)

砷•bronzing •pyrotechnics•doping agent in solid-state devices such as transistors •the arsenide is used as a laser material to convert electricity directly into coherent light

Sulfur Isotopes

Frasch Process for Extracting

Sulfur

Sulfuric Acid

• concentrated (large amount of solute)– strong acid– dehydrating agent– oxidizing agent

industrial production• by-product of roasting of sulfide ores or from

scrubbers in fossil fuel burning plants• produced from elemental sulfur by burning in air using

catalysis (contact process)

Properties of Sulfuric Acid

• concentrated (large amount of solute)– strong acid– dehydrating agent– oxidizing agent

Sulfuric Acid Production

S8(s) + 8O2(g) => 8SO2(g)

2 SO2(g) + O2(g) => 2 SO3(g)

SO3(g) + H2O(l) => H2SO4(aq)

Cu2Se + Na2CO3 + 2O2 2CuO + Na2SeO3 + CO2

The selenite Na2SeO3 is acidified with sulphuric

acid. Any tellurites precipitateout leaving selenous acid, H2SeO3, in solution. Selenium is

liberated from selenous acid by SO2

H2SeO3 + 2SO2 + H2O Se + 2H2SO4

Preparation of Se

Downs Cell

Chlor-Alkali Process

Production of Phosphorusin Electric Furnace

Phosphorus Allotropes

Industrial Preparation by Electrolysis

• Na+ + Cl- + H2O Na+ + 1/2Cl2 + 1/2H2 + OH-

Laboratory Preparation

MnO2 + 4HCl MnCl2 + Cl2 + 2H2O

Properties of Bromine

Atomic Number 35

Density (g/L) 3.12

Melting Point (oC) -7

Ionic Radius, Br-1 (pm) 196

Bromine and Iodine

Cl2 (g) + 2 Br- (aq) Br2 () + 2 Cl-

Cl2 (g) + 2 I- (aq) I2 (aq) + 2 Cl-

E° = +0.293 V

E° = +0.823 V

Laboratory Preparation:

NaBr (s) + H2SO4 (l) HBr (g) + NaHSO4 (s)

2HBr (g) + H2SO4 (l) Br2 (g) + SO2 (g) + 2H2O (l)

Bromine

•fumigants •flameproofing agents •water purification compounds •dyes •medicines • (AgBr) used for photography •pesticides •water purification •used to make plastics flame retardant

Properties of Iodine

Atomic Number 53

Density (g/L) 4.92

Melting Point (oC) 114

Ionic Radius, I-1 (pm) 220

•iodide, and thyroxin which contains iodine, are used internally in medicine. A solution of KI and iodine in alcohol is used as a disinfectant for external wounds. •silver iodide is used in photography •nutrient •added to table salt for nutrition {stops goitres, (Derbyshire neck)} •deep blue colour in a starch solution is a sign of the free element

Hydrogen Halides HX

bond enthalpy of HX(kJ mol-1)

electron affinity of X(kJ mol-1)

hydration enthalpy of X-

(kJ mol-1)sum of these(kJ mol-1)

HF +562 -328 -506 -272

HCl +431 -349 -364 -282

HBr +366 -324 -335 -293

HI +299 -295 -293 -289

The Representative Elements: Group 5A Through 8A.

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