the representative elements: group 5a through 8a

The Representative Elements: Group 5A

Through 8A

Copyright © Houghton Mifflin Company. All rights reserved. 19a–2

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

Copyright © Houghton Mifflin Company. All rights reserved.

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


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

Use

•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

Documents

melting point oc

boiling point oc

atomic radius pm

ionic radius

selenous acid

density gl1

c 6casio3

nitric acid