1. Chapter 22 Chemistry of the Nonmetals

2. Nonmetals
Except for hydrogen, the nonmetals are found in the upper right-hand corner of the periodic chart.

3. Periodic Trends
Within a group, smaller atoms are more likely to form -bonds because they can get closer to other atoms.

4. Periodic Trends
As a result, CO2 contains two -bonds, and SiO2 is a network solid with only -bonds.

5. Hydrogen Discovered by Henry Cavendish (1731-1810) Three isotopes
Protium (1H)  99.98% of all hydrogen
Deuterium (2H)  0.016%
Tritium (3H)  Radioactive

6. Properties of Hydrogen
Unique
Does not belong to any group
Very low melting (-259C) and boiling (-253C) points
Very large bond enthalpies
Reacts slowly
Reactions are generally quite exothermic

7. Hydrogen Production
Commercially produced from reaction of methane (CH4) with steam at 1100C or carbon and steam above 1000C
CH4 (g) + H2O (g)  CO (g) + 3 H2 (g)
CO (g) + H2O (g)  CO2 (g) + H2 (g)
C (s) + H2O (g)  H2 (g) + CO (g)
Production from electrolysis of water not energy-efficient

8. Uses of Hydrogen
Most hydrogen used to produce ammonia (NH3) in the Haber process
Also used to produce methanol (CH3OH)
CO (g) + 2 H2 (g)  CH3OH (g)

9. Uses of Hydrogen 2 H2 (g) + O2 (g)  2 H2O (g) H = -483.6 kJ
Using hydrogen as a fuel would have many advantages:
Highly exothermic reaction
Water is only product
Problem: How will we make the H2?

10. Hydrides
Three types
Ionic
Metallic
Molecular

11. Ionic Hydrides
Formed between hydrogen and alkali metals or heavy alkaline earth metals (Ca, Sr, Ba)
Very strong bases and reducing agents
React readily with water, so must be stored free from moisture

12. Metallic Hydrides
Formed between hydrogen and transition metals, often in unusual ratios
e.g., TiH1.8
Retain electrical conductivity and other metallic properties

13. Molecular Hydrides Formed between hydrogen and nonmetals or metalloids
Usually gases or liquids at room temperature and normal atmospheric pressure

14. Noble Gases Extremely stable and unreactive
Liquid He (boiling point 4.2 K) used as a coolant
Ne used in electric signs
Ar used in light bulbs and as insulating gas between panes in thermal windows.

15. Xenon Compounds
Of all noble gases, Xe can be forced to form compounds most easily
KrF2 also known, but decomposes at -10C

16. Halogens Have outer electron configurations of ns2np5
Large electron affinities and ionization energies
Tend to accept one electron to form anion

17. Halogens All have -1 oxidation state
All but fluorine also have positive oxidation states up to +7 when bonded to more electronegative atoms

18. Properties of Halogens
Tend to be good oxidizers, due to their electronegativity
Can oxidize anions of halides below them on periodic chart

19. Properties of Halogens
Fluorine has unusually high reduction potential
It can easily oxidize water:
F2 (aq) + H2O (l)  2 HF (aq) + 1/2 O2 (g) E = 1.80 V

20. Uses of Halogens
Fluorine reacts to form fluorocarbon compounds used as lubricants, refrigerants and plastics.
Teflon is a polymer of fluorocarbons.

21. Uses of Halogens Chlorine is the most-used halogen. HCl Plastics
Bleaches
Water purification

22. Uses of Halogens Bromine is the anion for silver in photographic film.
KI is added to table salt as a dietary supplement.

23. Hydrogen Halides
Aqueous solutions of HCl, HBr, and HI are, of course, strong acids.
HF and HCl can be produced by reacting salts with H2SO4.
Br- and I- oxidize too easily, so one must use a weaker oxidizing acid, like H3PO4.

24. HF
Hydrofluoric acid reacts with silicates, components of most types of glass.
This reaction causes glass to etch.
Therefore, HF is usually stored in plastic containers.

25. Oxyacids and Oxyanions
Oxyacid strength increases with increasing oxidation number of central halogen
Oxyacids are strong oxidizers.
Oxyanions generally more stable than corresponding acids

26. Perchlorates
While generally quite stable, perchlorates become exceedingly strong oxidizers when heated, and are used as rocket fuel.

27. Oxygen Joseph Priestley discovered oxygen in 1774.
Lavoisier give it its name, which means “acid former.”
Most commercial oxygen is obtained from air.

28. Oxygen Exists as one of two allotropes, O2 and O3 (ozone)
Forms very strong bonds
Reactions of oxygen-containing compounds have high activation energies
Reactions can be very exothermic, even to point of being explosive

29. Uses of Oxygen Oxidizing agent Bleach pulp and paper Medical uses
Welding (with acetylene)

30. Ozone Bluish gas with sharp odor
Extremely irritating to respiratory system
Stronger oxidizer than O2
Used to purify water
Used in organic synthesis
Absorbs UV light in upper atmosphere

31. Oxides Oxygen is second-most electronegative element
Always has negative oxidation state except when bonded to F
Acidic oxides like SO2 and SO3 form acids when exposed to water.
Basic oxides like BaO form hydroxide ion when they react with water.

32. Peroxides Oxygen has oxidation state of -1 O-O bond very weak
Decomposition of peroxides can be dangerously exothermic

33. Superoxides Oxygen has oxidation state of -1/2
The most active metals (K, Rb, Cs) form superoxides through reaction with O2
React with H2O to form O2
Source of O2 in self-contained breathing devices

34. Other Group 6A Elements
Have oxidation states of -2 as well as several positive oxidation states
Can have expanded octets

35. Selenium and Tellurium
Anions in minerals with Cu, Pb, Ag, and Au
Found as helical chains of atoms
Selenium not electrically conductive in dark, but quite so in light
Used in light meters, photosensors, and photocopiers

36. Sulfur Solid, yellow compound found in 8-membered ring
As heated to melting, ring breaks and sulfur becomes viscous, reddish-brown liquid

37. Sulfur
Most sulfur used for H2SO4 and for vulcanization of rubber

38. Pyrites Contain disulfide ion, S22-, the sulfur analog of peroxide
Found in minerals like iron pyrite (fool’s gold)

39. Sulfides
To say that many sulfides have rather unpleasant odors is a gross understatement.
H2S is emitted by rotten eggs.
Many minerals like galena (PbS) and cinnabar (HgS) are sulfides.

40. Sulfur Oxides, Oxyacids, and Oxyanions
SO2 is a poison, particularly to lower organisms.
Used to sterilize dried fruit and wine
Dissolves in H2O to form H2SO3
Sulfites and bisulfites added to foods and wines to kill bacteria

41. Sulfur Oxides, Oxyacids, and Oxyanions
Sulfuric acid
Strong acid
Good dehydrating agent
Decent oxidizer

42. Sulfur Oxides, Oxyacids, and Oxyanions
Thiosulfate ion resembles sulfate ion (a S replaces one of the O’s in sulfate)
Sodium thiosulfate pentahydrate (Na2S2O35 H2O) used in photography to remove unexposed AgBr from film as soluble complex of thiosulfate
Sulfate
Thiosulfate

43. Nitrogen Discovered in 1772 by Daniel Rutherford
Makes up 78% of Earth’s atmosphere
Can exist in oxidation states from -3 to +5

44. Nitrogen Many nitrogen-containing compounds strong oxidizers
N2 made into NH3 in Haber process
NH3 is precursor to many other compounds

45. Ammonia Hydrazines made from ammonia
One intermediate is chloramine (NH2Cl), poisonous compound produced when household ammonia and hypochlorite ion in bleach are mixed
Hydrazines are strong oxidizers used in rocket fuels

46. Oxides and Oxyacids
Nitrous oxide (N2O; laughing gas) was the first general anesthetic.
It is also used in aerosol products like whipped cream.

47. Oxides and Oxyacids
Nitric oxide (NO) is a slightly toxic, colorless gas.
Recently shown to be neurotransmitter in humans involved in vasodilation
Reacts with O2 in air to produce nitrogen dioxide, NO2

48. Oxides and Oxyacids Nitric acid Nitrous acid Strong acid and oxidizer
Used in fertilizer and explosive production (TNT, nitrocellulose, nitroglycerine)
Nitrous acid
Less stable, yet weaker acid than HNO3

49. Other Group 5A Elements
This group contains nonmetals (N and P), a metal (Bi), and metalloids (As and Sb).

50. Phosphorus Two allotropes White phosphorus (P4) Red phosphorus
Highly strained
Bursts into flames if exposed to O2 in air
Red phosphorus
Very stable

51. Oxyphosphorus Compounds
Phosphorus(III) oxide (P4O6) and phosphorus(V) oxide (P4O10) are anhydride forms of phosphorous (H3PO3) and phosphoric (H3PO4) acids

52. Oxyphosphorus Compounds
These acids condense to form polymeric forms.
Phosphoric acid and phosphates are found in detergents, fertilizers, and important biomolecules like DNA, RNA, and ATP.

53. Carbon Exists as four allotropes:
Graphite
Diamond
Fullerenes
Carbon nanotubules
Graphite converted to diamond (at 100,000 atm and 3000C) for industrial uses

54. Carbon Oxides Carbon monoxide (CO) Carbon dioxide (CO2)
Odorless, colorless gas
Binds preferentially to iron in hemoglobin, inhibiting O2 transport
Used as fuel, reducing agent in metallurgy, and precursor to organic compounds
Carbon dioxide (CO2)
Used to carbonate beverages, decaffeinate products (in its supercritical form) and as a refrigerant (as Dry IceTM)

55. Carbonic Acid and Carbonates
Dissolved CO2 in water is in equilibrium with carbonic acid, H2CO3
Carbonates found as minerals like calcite, CaCO3, the primary constituent of limestone

56. Silicon Second most abundant element in Earth’s crust
Semiconductor used in making transistors and solar cells
Purified by zone-refining

57. Silicates Have a central silicon surrounded by 4 oxygens
In disilicate, two tetrahedral structures share one oxygen
Silicate
Disilicate

58. Silicates These units can further connect into sheets or strands.
Talc and asbestos are two examples of molecules containing these structures.

59. Boron The only nonmetallic Group 3A element
Compounds of boron and hydrogen are called boranes.
Because boron does not have a filled octet, structures such as diborane, in which two borons share one hydrogen are possible.

60. Boron
Borane anions, such as borohydride, BH4-, are good reducing agents and sources of hydride ion.