Lead (Pb),
What do we really know about Pb?
Andrew Cheatwood
1/9/11
Lead (Pb), an element that almost all of us have heard of, but what do we really know
about Pb (“Introductory Chemistry”)? Lead is in many of the things we use every day. In fact,
almost every electronic you can get your hands on contains some amount of lead. Although,
Lead is infamous for its poisonous properties, little is known about its history, physical
characteristics, chemical properties, how it is obtained, effects on the environment, and other
interesting things.
Who discovered lead, where it was first found, and the exact date it was discovered is
unknown, but its utilization can be traced back to ancient times (“E-goldprospecting”). In fact,
the ancient Romans used lead to make water pipes. The fall of the Roman Empire has been
blamed, in part, on lead in the water supply (Gagnon). Lead coins and sculpture have been found
in Egyptian tombs dating back to 5000 B.C. (“A Guide to the Elements”). Lead’s chemical
symbol (Pb) comes from the Latin word for waterworks, plumbum (Gagnon). The actual name
lead comes from the Anglo-Saxon word “lead” (Gagnon). Lead is a metal with an atomic number
of eighty-two and a true atomic mass of 207.2 amu (Holding). Lead has a light gray to a slight
bluish grey color (“E-goldprospecting”). It has a hardness of 1.5 (“E-goldprospecting”). Its
streak is light gray and shiny (“E-goldprospecting”). Its luster is metallic and it has no cleavage
(“E-goldprospecting”). Its density is 11.4 g/cm3 and its tenacity is malleable/ductile (“Egoldprospecting”). Lead has a melting point of 600.61 K and a boiling point of 2022 K
(Gagnon). Lead is usually found as a solid at 298K or 76.73 degrees Fahrenheit.
Lead is usually extracted together with zinc, silver and copper from ores (Holding). Galena is
the most commonly used ore for the extraction of lead (Holding). It can also be obtained from
ores like cerrussite and anglesite (Holding). Galena is mined in Australia, which produces 19%
of the world's new lead, followed by the United States of America, China, Peru and Canada
(Holding). Its estimated crustal abundance is 1.4×101 milligrams per kilogram and its Estimated
Oceanic Abundance is 3×10-5 milligrams per liter (Gagnon).
Lead’s atomic radius is 1.81Å and its atomic volume is 18.17cm3/mol. Its covalent radius is
1.47Å and its crystal structure is cubic face centered. Its electron configuration is 1s2 2s2p6
3s2p6d10 4s2p6d10f14 5s2p6d10 6s2p2 (Barbalace). To determine the number of valence electrons see
electron dot diagram (Appendix C). Lead’s minimum oxidation number is -4 and its minimum
common oxidation number is 0. Lead’s maximum oxidation number is +4 and its maximum
common oxidation number is +4 (Lead Element Facts). Lead has 35 isotopes whose half-lives
are known, mass numbers 181 to 215 (Lead Element Facts). Of these, only three are stable:
206
Pb, 207Pb and 208Pb (Lead Element Facts) (see appendix A). When lead reacts with mild air, ⇒
PbO. When it reacts with 15 M HNO3: mild, ⇒ NOx, Pb(NO3)2. Some oxides of lead include
PbO, PbO2, Pb2O3, and Pb3O4. Some chlorides include PbCl2 and PbCl4. One of lead’s hydrides
is PbH4 (Lead Element Facts).
The extraction of lead from galena is a fairly simple process. The finely powdered ore is
concentrated by froth floatation process. It then goes through a self reduction process
(“Transtutors”). The concentrated ore is then heated in air (“Transtutors”). Lead sulfide is
partially converted into lead oxide and lead sulphate (“Transtutors”). 2PbS + 3O2 ——> 2 PbO +
2SO2 and PbS + 2O2 ——> PbSO4 (“Transtutors”). The supply of air is cut off and the
temperature is raised (“Transtutors”). The galena then reduces both PbO and PbSO4 to metallic
lead (“Transtutors”). PbS + 2PbO ——> 3Pb + SO2 and PbS + PbSO4 ——> 2Pb + 2SO2
(“Transtutors”).
One monumental use of lead is lead glass. Medically, lead glass can be used for X-ray
observation equipment, electron beam/plasma generators and X-ray TV detectors (“Scientific,
Direct”). Lead glass protects doctors and staff from X-ray irradiation with no glass discoloration
or deterioration in viewing quality (“Scientific, Direct”). Industrially, lead glass is used to protect
people from airport luggage inspection equipment, and from radiation testing equipment or
radioactive industrial products at industrial sites (“Scientific, Direct”). Lead is used in many
other things as well. For example: large quantities of lead, both as the metal and as the dioxide,
are used in storage batteries (“Lead Element Facts”). Lead is also used in cable covering, as
ammunition, as electrodes, in solder and as roofing material (“Lead Element Facts”). The metal
is used as shielding from radiation, e.g. in x-ray rooms and nuclear reactors (“Lead Element
Facts”). Lead oxide is also used in the manufacture of fine crystal glass (“Lead Element Facts”).
Historically, lead was used in plumbing (“Lead Element Facts”). Tetraethyl lead was used as an
anti-knock agent in gasoline, and as an additive in paints (“Lead Element Facts”). These uses
have been reduced recently because of environmental concerns about cumulative lead poisoning
(“Lead Element Facts”).
Lead is tremendously important to the world economy. As a pure element, lead cost around
$2.45 per 100 grams (“Lead Element Facts”). By the early 2000s, the total demand for lead in all
types of lead-acid storage batteries represented 88% of apparent U.S. lead consumption (Survey,
U.S. Geological). Other significant uses included ammunition (3%), oxides in glass and ceramics
(3%), casting metals (2%), and sheet lead (1%) (“Survey, U.S. Geological”). The remainder was
consumed in solders, bearing metals, brass and bronze billets, covering for cable, caulking lead,
and extruded products (“Survey, U.S. Geological”). The value of recoverable mined lead in
2008, based on the average U.S. producer price, was $1.23 billion (“Survey, U.S. Geological”).
As useful as lead is it can have some detrimental effects on the environment (Holding).
Activities, such as fuel combustion, industrial processes and solid waste combustion can
contribute to lead in the environment (Holding). Lead can end up in water and soil through
corrosion of leaded pipelines in a water transporting system and through corrosion of leaded
paints (Holding). It cannot be broken down; it can only be converted into other forms (Holding).
Lead accumulates in the bodies of water organisms and soil organisms. These will experience
health effects from lead poisoning (Holding). Health effects on shellfish can take place even
when only very small concentrations of lead are present (Holding). Body functions of
phytoplankton can be disturbed when lead interferes (Holding). Phytoplankton is an important
source of oxygen production in seas and many larger sea-animals eat it (Holding). That is why
we now begin to wonder whether lead pollution can influence global balances (Holding). Soil
functions are disturbed by lead intervention, especially near highways and farmlands, where
extreme concentrations may be present (Holding). Soil organisms suffer from lead poisoning, too
(Holding). Lead is a particularly dangerous chemical, as it can accumulate in individual
organisms, but also in entire food chains (Holding).
Not only can lead affect the health of animals, but lead can also have damaging effects on the
human body and health (“E-goldprospecting”). It can enter the body through food, water, and the
air (“E-goldprospecting”). Foods like fruit, vegetables, meats, grains, seafood, soft drinks and
wine may contain significant amounts of lead (“E-goldprospecting”). Small traces of lead can be
found in cigarette smoke (“E-goldprospecting”). Lead can enter drinking water when pipes rust
or corrode (“E-goldprospecting”). Lead can have damaging effects on the human body and
health (“E-goldprospecting”). For example: disruption of the biosynthesis of hemoglobin and
anemia, a rise in blood pressure, kidney damage, miscarriages and subtle abortions, disruption of
nervous systems, brain damage, declined fertility of men through sperm damage, diminished
learning abilities of children, behavioral disruptions of children, such as aggression, impulsive
behavior and hyperactivity (“E-goldprospecting”).
Separating lead (II) ions from barium and tin ions is fairly simple (“Solubility/Insolubility
Chart”). Before beginning the seperation process make sure to take the appropriate saftey
precautions. As is costumary goggles, gloves, and aprons, must be worn at all times in case of
spills, broken glass, fire, etc. If a spill does occur immediately wash hands and/or clothing to
remove any harmful chemicals, and report the incident to the teacher in charge, or present at the
time. Begin by putting iodine (I1- ) into the solution (“Solubility/Insolubility Chart”). It will
separate the lead (II) ions from the solution creating insoluble plumbous iodide (PbI2 ) and
leaving the barium and tin ions in the solution (“Solubility/Insolubility Chart”). Next, put sulfate
(SO42-) in to barium and tin ion solution (“Solubility/Insolubility Chart”). Doing this will
separate the barium ions from the tin ions creating insoluble barium sulfate (BaSO4) and leaving
tin (“Solubility/Insolubility Chart”). Vis versa the tin ions can be separated from the barium ions
by placing sulfur in to the solution of barium and tin ions (“Solubility/Insolubility Chart”). Doing
this will create insoluble stannous sulfide (SnS) and leave barium (“Solubility/Insolubility
Chart”).
Works Cited
B.V, Holding. Lenntech Water treatment & purification . 1998-2009. 27 October 2010
<http://www.lenntech.com/periodic/elements/pb.htm>.
Barbalace, Kenneth L. environmentalchemistry . 1995 - 2010 . 13 December 2010
<http://environmentalchemistry.com/yogi/periodic/Pb.html>.
"The Names and Symbols of the Most Common Elements." Decoste, Zumdahl. Introductory
Chemistry . Boston, MA: Houghton Mifflin Company , 2008. 77.
Gagnon, Steve. It's Elemental - The Element Lead. 3 December 2010
<http://education.jlab.org/itselemental/ele082.html>.
Lead Element Facts . 14 December 2010 <http://www.chemicool.com/elements/lead.html>.
Scientific, Direct. drct. 14 December 2010
<http://www.drct.com/dss/Lead_glass/lead_glass.htm>.
Solubility/Insolubility Chart. 15 December 2010
<http://www.saltlakemetals.com/Solubility_Chart.htm>.
"Lead ." Stwertka, Albert. A Guide to the Elements . New York, New York : Oxford University
Press , 2002. 186.
Survey, U.S. Geological. metalprices. January 2009. 13 December 2010
<http://www.metalprices.com/FreeSite/metals/pb/pb.asp>.
Ttranstutors. 2010-2011 . 14 December 2010 <http://www.transtutors.com/chemistryhomework-help/S-and-P-block-elements/extraction-and-refining-of-lead.aspx>.
Appendix
A
(Gagnon)
B
(Solubility/Insolubility Chart)
C