Nonmetals
• Except for hydrogen, the nonmetals are found in the upper right‐hand corner of the periodic chart.
Chemistry of the Nonmetals
Chapter 20
Chemistry: The Central Science 3rd Edition (Australian Edition)
Brown, LeMay, Bursten, Murphy, Woodward, Langford, Sagatys, & George Periodic Trends
• Within a group, smaller atoms are more likely to form ‐
bonds because they can get closer to other atoms.
Periodic Trends
• As a result, CO2
contains two ‐bonds, and SiO2 is a network solid with only ‐
bonds.
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Hydrogen
Properties of Hydrogen
• First isolated by Henry Cavendish (1731‐1810)
• Antoine Lavoisier named it hydrogen
• Most abundant element in the universe
• Most hydrogen on earth is bound to oxygen (H2O)
• There are 3 natural isotopes of hydrogen
• Can be found above Li in the periodic table
– Forms + ion less readily than Li
– Ionisation energy ~ 1312 (vs 520 for Li) kJ mol‐1
• Can be placed above F in the periodic table
– Can form a negative ion (Hydride ion H ‐)
• H2 (dihydrogen or molecular hydrogen)
– Colourless, odourless, tasteless gas at room temperature
– Non‐polar, low m.p. & b.p. (‐259 and ‐
253 °C)
– High bond enthalpy but easily activated by heat, sparks, irradiation, or catalysts
– Reacts rapidly and exothermically with variety of substances
Preparation & Uses of Hydrogen
Industrial Scale Production via Steam Reforming of Natural Gas →
Can use coal (mostly carbon)
→
Water Electrolysis
→
• Ionic Hydrides
– Alkali metals
– Also Ca, Sr, & Ba….electronegativity?
– Hydride ion H‐ is very basic, good reducing agent
• CaH2 + H2O  __?_+__?____
• CO + H2 = Water Gas
• Water gas used to make fuels & other hydrocarbons • SASOL – CTL technologies
Re‐write the natural gas and steam rxn with water gas as the product
Binary Hydrogen Compounds
• Metallic Hydrides
– Transition metals and H2
– Can form non‐stoichiometric compounds e.g. TiH1.8
– Can be described as a solution of hydrogen atoms in a metal – embrittlement
– Pd important industrially
• Molecular Hydrides
– Non metals and semi‐metals
Main uses include, Ammonia synthesis, Petrochemical industry, Metallurgical processes
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Hydrogen Economy
Oxygen
• Joseph Priestley discovered oxygen in 1774.
• Lavoisier gave it its name, which means “acid former.”
• Most commercial oxygen is obtained from air.
Properties of Oxygen
• It has two allotropes, O2 and O3 (ozone)
• Colourless odourless gas
– m.p. ‐218 °C, and b.p. ‐183 °C
– Slightly soluble in water
– Can accept or share two electrons
[He] 2s2 2p4
Uses and Preparation of Oxygen
Uses
Preparation
• Oxidizing agent
• Commercially – Bleach pulp and paper
– Medical uses
– Welding (with acetylene)
– Liquefied air
• It forms very strong bonds
– Reactions of oxygen‐containing compounds have high activation energies.
– Reactions can be very exothermic, even to the point of being explosive.
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Oxides
Ozone
• Oxygen is second‐most electronegative element
– Always has negative oxidation state except when bonded to F.
• Bluish gas with sharp odor.
• Extremely irritating to respiratory system.
• Stronger oxidiser than O2
– Used to purify water.
• Acidic oxides like SO2 and SO3 form acids when exposed to water.
SO2 (g) + H2O (l)  H2SO4 (aq)
• Basic oxides like BaO form hydroxide ion when they react with water.
BaO (s) + H2O (l)  ? (aq)
• Used in organic synthesis.
• Absorbs UV light in upper atmosphere.
Superoxides
• Oxygen has oxidation state of ‐½
• The most active metals (K, Rb, Cs) form superoxides through reaction with O2
Metals with variable oxidation states show a decrease in basic character as the oxidation state increases
Peroxides
• Here oxygen has an oxidation state of ‐1
• Na, Ca, Sr, & Ba form peroxides
• React with H2O to form O2
– Source of O2 in self‐contained breathing devices.
• The O‐O bond is very weak
– Decomposition of peroxides can be dangerously exothermic
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Other Group 16 Elements
• Have oxidation states of ‐2 as well as several positive oxidation states.
ns2 np4
• Can have expanded octets.
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.
Sulfur
• Solid, yellow compound found in 8‐
membered ring.
• As heated to melting, ring breaks and sulfur becomes viscous, reddish‐brown liquid.
Sulfur
• Most of the sulfur is used for the production of H2SO4 and for the vulcanisation of rubber.
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Sulfides
• Contain disulfide ion, S22‐, the sulfur analogue of peroxide.
• Found in minerals like iron pyrite (fool’s gold), PbS (galena), & HgS
(cinnabar).
• Many sulfides have rather unpleasant odours
Sulfur Oxides, Oxyacids and Oxyanions
• SO2 is a poison, particularly to lower organisms
– Used to sterilise dried fruit and wine
– Dissolves in H2O to form H2SO3
• Sulfites and bisulfites are added to foods and wines to kill bacteria.
– H2S is emitted by rotten eggs.
Production of Sulfuric Acid (Contact Process)
Sulfur or an ore of sulfur oxidised in excess air
S s
AFeS2 s
O2 g →SO2 g
QO2 g →WFeyOx ZSO2 g
Sulfur Oxides, Oxyacids and Oxyanions
• Sulfuric acid
– Strong acid
– Good dehydrating agent
– Decent oxidiser!
Converting the sulfur dioxide into sulfur trioxide
V2O5
@
450 °C
2SO g
O2 g ⇌ SO3 g
∆ Dissolving the sulfur trioxide in sulfuric acid
SO g
SO4 l →
O l
Dissolving the oleum in water
O l
O l →
Oleum
• manufacture of fertilizers, explosives, dyes, petroleum products, domestic acidic drain cleaner, lead‐acid batteries, mineral processing, fertilizer manufacturing, oil refining, wastewater processing, and chemical synthesis. • Industrial Barometer
SO4 l
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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.
Nitrogen
• Discovered in 1772 by Daniel Rutherford.
• Makes up 78% of Earth’s atmosphere.
• Can exist in oxidation states from ‐3 to +5.
Nitrogen
• Many nitrogen‐containing compounds are strong oxidisers.
• N2 is made into NH3 via the Haber process
– NH3 is precursor to many other compounds.
Ammonia
Haber Process
N2 (g) + 3 H2 (g)  2 NH3 (g)
150 – 250 bar, 300 – 550 °C
Fe‐based catalysts
• Hydrazines made from ammonia
– One intermediate is chloramine (NH2Cl), a poisonous compound produced when household ammonia and hypochlorite ion in bleach are mixed.
• Hydrazines are strong oxidisers
– used in rocket fuels.
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Oxides and Oxyacids
• Nitrous oxide (N2O, laughing gas) was the first general anaesthetic.
Oxides and Oxyacids
• Nitric oxide (NO) is a slightly toxic, colourless gas
– recently shown to be neurotransmitter in humans
– involved in vascodilation
• Reacts with O2 in air to produce nitrogen dioxide, NO2
• It is also used in aerosol products like whipped cream.
Oxides and Oxyacids
• Nitric acid
Ostwald Process
Ammonia is oxidised to NO gas (850 °C & Pt based catalyst)
4NH
– Strong acid and oxidiser
– Used in fertiliser and explosive production (TNT, nitrocellulose, nitroglycerine)
5O
→ 4NO
6H O
NO gas converted to NO2
2NO
O
→ 2NO
NO2 Dissolved in water
• Nitrous acid
– Less stable, yet weaker acid than HNO3
3NO
H O
→ NO
2H
2NO
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Phosphorus
Other Group 15 Elements
• This group contains nonmetals (N and P), a metal (Bi), and metalloids (As and Sb).
• Two allotropes
– White phosphorus (P4)
• Highly strained
• Bursts into flames if exposed to O2 in air
– Red phosphorus
• Very stable
Oxyphosphorus Compounds
• Phosphorus(III) oxide (P4O6) and phosphorus(V) oxide (P4O10) are anhydride forms of phosphorous (H3PO3) and phosphoric (H3PO4) acids.
Oxyphosphorus Compounds
• These acids condense to form polymeric forms.
• Phosphoric acid and phosphates are found in detergents, fertilisers and important biomolecules like DNA, RNA, and ATP.
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Carbon
• Exists as four allotropes
–
–
–
–
Graphite
Diamond
Fullerenes
Carbon nanotubules
• Graphite converted to diamond (at 100,000 atm and 3000C) for industrial uses.
Oxides of Carbon
• Carbon monoxide (CO)
– Odourless, colourless gas
– Binds preferentially to iron in haemoglobin, 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 Ice )
TM
Carbonic Acid and Carbonates
Other Inorganic Carbon
• Dissolved CO2 in water is in equilibrium with carbonic acid, H2CO3.
• Carbonates found as minerals like calcite, CaCO3, the primary constituent of limestone.
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Carbon Composites
Silicon
• Second most abundant element in Earth’s crust.
• Semiconductor used in making transistors and solar cells.
• Purified by zone‐
refining.
Figure 17.35
Silicates
Silicates
• Have a central silicon surrounded by 4 oxygens.
• In disilicate, two tetrahedral structures share one oxygen.
• These units can further connect into sheets or strands.
Figure 17.37
• Talc and asbestos are two examples of molecules containing these structures.
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Boron
• The only nonmetallic Group 13 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.
Boron
• Borane anions, such as borohydride, BH4‐, are good reducing agents and sources of hydride ion.
• The only important oxide of boron is boric oxide, B2O3, which is the anhydride of the very weak acid, H3BO3 (boric acid).
• The diprotic acid H2B4O7 is called tetraboric acid and its hydrated sodium salt Na2B4O7H2O is borax.
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