Lead

Lead (Pb)

Introduction

Lead is a chemical element with atomic number 82 in the periodic table. It’s available in Earth’s crust at 14 ppm and is typically found in the form of several different lead ores. This lustrous heavy metal has four valence electrons and the heaviest stable atom among all other elements of Mendeleev’s system. 

Element 82 is one of the most toxic chemical elements as well as one of the main environmental pollutants. But, despite its toxicity, lead has a wide industrial application. 

Fact Box

Chemical and Physical Properties of Lead

The symbol in the periodic table of elements: Pb

Atomic number: 82

Atomic weight (mass): 

Group number: 14 (Heavy metal)

Period: 6 (p-block)

Color: A silvery-grey lustrous metal with a bluish-white hue

Physical state: Solid at room temperature

Half-life: From 0.23(15) milliseconds to 2.01×1019 years

Electronegativity according to Pauling: 1.8

Density: 11.3 g.cm−3 at 20°C

Melting point: 327.462°C, 621.432°F, 600.612 K

Boiling point: 1749°C, 3180°F, 2022 K

Van der Waals radius: 0.154 nm

Ionic radius: 0.132 nm (+2); 0.084 nm (+4)

Isotopes: 43

Most characteristic isotope: 204Pb, 206Pb, 207Pb, and 208Pb

Electronic shell: [Xe] 4f145d106s26p2

The energy of the first ionization: 715.4 kJ.mol-1

The energy of the second ionization: 1450.0 kJ.mo-1

The energy of the third ionization: 3080.7 kJ.mol-1

The energy of the fourth ionization: 4082.3 kJ.mol-1

The energy of the fifth ionization: 6608 kJ.mol-1

Discovery date: Unknown; in ancient times

With the periodic table symbol Pb, atomic number 82, atomic mass of X g.mol-1, and electron configuration X, lead is very soft, ductile, and malleable silvery-gray by color. It reaches its boiling point at 1749°C, 3180°F, 2022 K, while the melting point is achieved at 327.462°C, 621.432°F, 600.612 K. 

Unlike many other metals, lead is not a good conductor of electricity. It’s corrosion-resistant, but tarnishes upon exposure to air and changes its color from lustrous silver to dull gray. Lead has an electronegativity of 1.8 according to Pauling, whereas the atomic radius according to van der Waals is 0.154 nm.                         

How Was Lead Discovered?

Known since ancient times, lead was very likely discovered along with silver since they often occur in the same mineral ores. The first record evidence of lead’s existence was found in the library of the Assyrian king Ashurbanipal (668-626 BC). Allegedly, one of the Babylonian scripts contains the verses “You melt Copper and Lead, you clean Gold and Silver.” This is a clear reference to the process of lead isolation from the ores. 

Easy to be extracted and worked with, lead has been widely used by the ancient civilization, especially the Romans. They differentiated lead (Pb) from tin (Sn) by using the expression ‘plumbum nigrum’ (black lead) for element 82, and ‘plumbum album’ (white lead) for element 50. In today’s classification of the chemical elements in the periodic table by Mendeleev, tin is placed directly above lead. 

The first thing they learned about this heavy metal is that it’s very poisonous. The ancient people became aware of this after more and more lead miners fell ill and perished upon exposure to this chemical after a short while. Consequently, they forced prisoners and slaves to do the lead mining instead.

The most notable use of this metal by the Romans was for plumbing, hence its name. Also, they were producing various other everyday items of it, such as coins, statues decorating their garden paths, glazes, glasses, enamels, utensils, even some types of weapons.

Even the ancient alchemists were intrigued by this chemical. In the Middle Ages, alchemy was a combination of science, philosophy, medicine, and mysticism. Believing that precious metals were the perfect elixir of life, the alchemists of that time were using this metal as their “philosopher’s stone” which was their definition of lead.  In an attempt to turn this ordinary metal into gold, the alchemist used the process of chrysopoeia (Greek: transmutation). 

How Did Lead Get Its Name?

The name of this chemical element originates from the Anglo-Saxon words ‘lead‘, the Middle English “leed”(lede), and Old English “lēad”, all denoting metal. The symbol Pb of lead was derived from the ancient Romans and their practice to use lead pipes for plumbing. Hence, the symbol Pb for lead was derived from the Latin word ‘from the Latin ‘plumbum’ associated with the first known practical use of this metal. 

Where Can You Find Lead?

The pure, elemental form of lead can be rarely found in nature. It mostly occurs in zinc, copper, and silver ores. The primary lead ore is the mineral galena (PbS). This natural form of the lead sulfide mineral occurs as a component of the minerals sphalerite, anglesite, tennantite-tetrahedrite, cerussite, minum, pyrite, chalcopyrite, skarns, as well as in the sedimentary rocks. Due to its distinct silver color and metallic luster, galena is easy to be identified in sedimentary, igneous, and metamorphic rocks. 

Typically, galena (PbS) comprises 86.6% lead and 13.4% sulfur. In some cases, it may contain a significant amount of silver in place of the lead. Also, this lead sulfide mineral may incorporate traces of antimony, bismuth, zinc, cadmium, arsenic, and copper in its structure.

The smelting process of galena is a relatively easy one. Namely, if galena containing rock is exposed to fire, the pure lead would remain in the ashes of the mineral. This heavy metal can also be obtained through the recycling process. 

The world’s largest lead-producing countries are China, Australia, United States, Peru, Russia, Mexico, and India.

Lead in Everyday Life

Known since ancient times, lead has a wide application in many industries and manufacturing processes of many everyday products in our times, too. However, due to its toxicity and negative effect upon our environment, it’s been gradually phased out of use.

Today, this chemical element finds use in the following instances:

  • Almost all paints and surface coating materials contain lead in some percent, even children’s toys; lead chromate (PbCrO4), also known as crocoite, is typically used in the manufacturing of chrome yellow paint;
  • The high density of lead makes this heavy metal an efficient shield against x-rays and gamma-ray radiation;
  • Ceramic glazes and stained glass contain lead in some percent;
  • Some plumbing pipes are made of lead which can contaminate the drinking water over time;
  • Leed sheets were used for roofing, for the roof parapets, gutters, and gutter joints, and as an antiknock compound in gasoline. However, today this is no longer the practice due to lead’s toxicity.  
  • Fireworks and other pyrotechnics are produced with lead nitrate (Pb(NO3)2) as one of the main components;
  • A lead, tin, and antimony alloy is applied in the production of printing presses and plates;
  • As one of the main components in the manufacturing process of glass for computer and television screens, leads’ role is to serve as radiation protector of the viewer;
  • Lead is used in the electrodes which are applied in the process of electrolysis;
  • The lead alloy labeled as babbit is commonly used for the reduction of friction in bearings;
  • Tetraethyl lead (PbEt4) is still used for some petrol grades, but more and more it’s replaced by a more ecological type of petrol that does not contain lead as one of the ecological measures against pollution;
  • Lead can be found in some cosmetic products, toys, imitation jewelry, vinyl products, etc.
  • Lead monoxide (PbO), or litharge, has an application in the making of lead crystal, flint glass, and the vulcanization of rubber process;
  • Famously, lead is used for manufacturing of projectiles and ammunition, as well as for the weight in sports equipment;
  • This metal has a wide application in the making of lead fishing sinkers and curtain weights;
  • Lead-acid batteries are used in cars, trucks, motorcycles, boats, and other motorized equipment.

Lead and Health

Many years ago, ancient medical practitioners were using lead oxide for various diseases. Typically they were added to ointments and lotions for the treatment of skin diseases, corns, and bunions. However, today’s advanced medicine and science provide reliable evidence of lead being one of the most harmful chemicals for human health even at low levels of accumulation. 

Lead can enter our body through contaminated air, food, water from leaded pipes, as well as unregulated cosmetics and medicines. Prolonged exposure to high levels of this heavy metal and its compounds can cause irreversible neurological damage, mental retardation in children, cardiovascular problems, fertility problems in both men and women, birth defects, and other severe health problems.

During pregnancy, the damaging effects of lead can affect the brain development of a fetus and cause learning and behavior problems by damaging the central nervous system. If the particles of lead dust are inhaled, they may cause severe damage to the lungs.

What Has Tobacco Got to Do with Lead?

In addition to the addictive ingredient nicotine, a tobacco cigarette typically contains other toxic substances and heavy metals, such as:

  • Lead [both radioactive (Pb-210) and non-radioactive (Pb-206) isotope];
  • Tar;
  • Cadmium;
  • Chromium;
  • Copper;
  • Mercury;
  • Nickel;
  • Zinc;
  • Hydrogen cyanide;
  • Formaldehyde;
  • Arsenic;
  • Ammonia;
  • The radioactive polonium-210 isotope;
  • Benzene;
  • Carbon monoxide;
  • Tobacco-specific nitrosamines (TSNAs);
  • Polycyclic aromatic hydrocarbons (PAHs);
  • Carcinogen nitrates and nitrites.

All of the aforementioned substances are some of the most potent cancer-causing chemicals that lead to adverse health effects and severe health risks, including:

  • Chronic Obstructive Pulmonary Disease (COPD);
  • Lung infections (pneumonia and tuberculosis);
  • Asthma;
  • Chronic bronchitis;
  • Emphysema;
  • Coronary Heart Disease (CHD);
  • Peripheral Arterial Disease (PAD);
  • Aortic Aneurysm;
  • Increased risk of cataract (clouding of the lenses of the eyes);
  • Risk of type 2 diabetes;
  • Elevated blood pressure values;
  • Bleeding gums;
  • Increased (bad) cholesterol levels;
  • Lowered immunological defense of the body;
  • Vitamin depletion of the body (especially Vitamins C, D, and E);
  • Heart attack; 
  • Stroke,
  • Cancer of all the body’s organs and tissues;
  • Vision problems (increased risk of cataract development, glaucoma, diabetic retinopathy).

Pregnant women exposed to lead from tobacco smoke have a greater risk of ectopic pregnancy, risk of preterm delivery, giving birth to a fetus with severe damage of the lungs, and central nervous system, low birth-weight babies, etc. 

The Center for Disease Control and Prevention (CDC) had classified cigarette smoking as a number one risk of lung cancer. Upon inhalation of the cigarette smoke, some of the radioactive Pb-210 quantities remain absorbed in the lungs, releasing radiation as this form of lead decays to the intensely radioactive carcinogen polonium-210. 

Even though the inhaled toxic substances primarily go to the lungs, cigarette smoking may cause cancer to any other organ or tissue of the body. 

Passive (Secondhand) Smoking and Lead Exposure

Secondhand or passive smoking is when a person breathes in other people’s smoke from the cigarettes. Passive smoking can be as dangerous as smoking because the person is exposed to the same toxic ingredients of the tobacco. 

What are the Health Risks of Passive (Secondhand) Smoking?

A study conducted by a team of scientists provides evidence that passive smoking, or secondhand tobacco smoke, is one of the main sources of lead exposure of children and adolescents in the United States. The study cites the findings according to which there’s a tight relation between young children and adolescents exposed to secondhand tobacco smoke and the increased blood lead levels. 

This involuntary exposure of the individuals to the toxic effect of lead, heavy metals, radioactive substances, and other carcinogen chemicals contained in the tobacco smoke heavy metals are at greater risk of having:

  • Weakened immune system;
  • Shortness of breath;
  • Reduced physical fitness;
  • Heightened risk of infections and colds;
  • Decreased sense of smell and taste;
  • Worsened chronic diseases;
  • Asthmatic attacks;
  • Cardiovascular diseases;
  • Irritability;
  • Nausea;
  • Headaches;
  • Respiratory infections;
  • Lung problems.

How Dangerous Is Lead?

According to the Agency for toxic substances and disease registry, The Department of Health and Human Services (HHS.gov), the U.S. Environmental Protection Agency (EPA), the National Institute for Occupational Safety and Health (NIOSH), and the International Agency for Research on Cancer (IARC), lead is classified as a cancerogenic substance. 

There are no safe levels of lead in the blood. Even the lowest absorbed quantity of this heavy metal may lead to irreversible neurological damage. When the blood lead levels are high, it may increase the risk of tumorous growth and cancer that can affect all systems of the body.

Lead Poisoning

Any level of lead concentration in blood is considered lead poisoning. The damages to the organs and tissues of the body are proportional to the serum levels of lead. Namely, the more lead is absorbed in the bloodstream, the greater the damage to the tissues is.  

Lead poisoning can occur via through occupational or environmental sources:

  • Environmental pollution;
  • Inhalation of lead particles generated by lead recycling, smelting, stripping leaded paint, burning of leaded gasoline or leaded aviation fuel;
  • Drinking water from leaded pipes;
  • Consuming food from lead-glazed or lead-soldered containers;
  • Consuming fruits or vegetables grown in lead-contaminated soil;
  • Excess tobacco smoking.

What Are the Symptoms of Lead Poisoning?

  • Coma;
  • Neurological problems;
  • Cognitive problems;
  • Anemia;
  • Hypertension;
  • Renal impairment;
  • Low immunological responses of the body;
  • Toxicity to the reproductive organs.

Environmental Effects of Lead

The widespread use of lead in everyday life has given this metal a “lead role” as one of the biggest pollutants that affect both public health and the environment. The largest lead concentrations found in the environment are a result of human activities, such as industrial processes, solid waste combustion, exhaust fumes of the cars fueled on lead petrol, etc.

Lead can contaminate the drinking water via the lead piping of the water supply system. This lead-contaminated water can also end up in the surface water where this heavy metal can accumulate in aquatic life and lead to their extermination. 

Measures for Limiting the Lead Exposure in the United States

According to EPA, the United States laws and regulations have limited the allowable level of lead in certain products or completely removed lead as a component of leaded gasoline, lead water pipes, lead paint, and lead plumbing fixtures over 40 years as part of the measure for both public health and environmental health protection. 

EPA has also regulated the toxic air pollutant emissions of lead manufacturers that affect drinking water, dust, soil, air, as well as waste disposal by a set of regulations labeled under the name National Emission Standards for Hazardous Air Pollutants, or NESHAPs. 

Primary Lead Smelting and Secondary Lead Smelting are two of the NESHAP’s regulations that address the limiting of lead emissions in the environment. 

Isotopes of Lead

The first Pb-204 isotope of lead is considered to be primordial, i.e. older than the Earth. Created in the Universe, this form of lead is slightly radioactive. It’s also one of the four stable isotopes of lead, a group also composed of 206Pb, 207Pb, and 208Pb.

The lead-206, lead-207, and lead-208 isotopes are found at the end of the three decay chains: the uranium series (radium), the actinium series, and the thorium series. 

Among the lead forms ranging from the atomic number 178Pb-218Pb, 209Pb isotope is the longest living lead isotope with a half-life of 2.01×1019 years. 

Nuclide[4]

[n 1]

Historic

name

Z N Isotopic mass (Da)[5]

[n 2][n 3]

Half-life Decay

mode

[n 4]

Daughter

isotope

[n 5][n 6]

Spin and

parity

[n 7][n 8]

Natural abundance (mole fraction)
Excitation energy[n 8] Normal proportion Range of variation
178Pb 82 96 178.003830(26) 0.23(15) ms α 174Hg 0+
179Pb 82 97 179.00215(21)# 3.9(1.1) ms α 175Hg (9/2−)
180Pb 82 98 179.997918(22) 4.5(11) ms α 176Hg 0+
181Pb 82 99 180.99662(10) 45(20) ms α (98%) 177Hg (9/2−)
β+ (2%) 181Tl
182Pb 82 100 181.992672(15) 60(40) ms

[55(+40−35) ms]

α (98%) 178Hg 0+
β+ (2%) 182Tl
183Pb 82 101 182.99187(3) 535(30) ms α (94%) 179Hg (3/2−)
β+ (6%) 183Tl
184Pb 82 102 183.988142(15) 490(25) ms α 180Hg 0+
β+ (rare) 184Tl
185Pb 82 103 184.987610(17) 6.3(4) s α 181Hg 3/2−
β+ (rare) 185Tl
186Pb 82 104 185.984239(12) 4.82(3) s α (56%) 182Hg 0+
β+ (44%) 186Tl
187Pb 82 105 186.983918(9) 15.2(3) s β+ 187Tl (3/2−)
α 183Hg
188Pb 82 106 187.980874(11) 25.5(1) s β+ (91.5%) 188Tl 0+
α (8.5%) 184Hg
189Pb 82 107 188.98081(4) 51(3) s β+ 189Tl (3/2−)
190Pb 82 108 189.978082(13) 71(1) s β+ (99.1%) 190Tl 0+
α (.9%) 186Hg
191Pb 82 109 190.97827(4) 1.33(8) min β+ (99.987%) 191Tl (3/2−)
α (.013%) 187Hg
192Pb 82 110 191.975785(14) 3.5(1) min β+ (99.99%) 192Tl 0+
α (.0061%) 188Hg
193Pb 82 111 192.97617(5) 5# min β+ 193Tl (3/2−)
194Pb 82 112 193.974012(19) 12.0(5) min β+ (100%) 194Tl 0+
α (7.3×10−6%) 190Hg
195Pb 82 113 194.974542(25) ~15 min β+ 195Tl 3/2#-
196Pb 82 114 195.972774(15) 37(3) min β+ 196Tl 0+
α (3×10−5%) 192Hg
197Pb 82 115 196.973431(6) 8.1(17) min β+ 197Tl 3/2−
198Pb 82 116 197.972034(16) 2.4(1) h β+ 198Tl 0+
199Pb 82 117 198.972917(28) 90(10) min β+ 199Tl 3/2−
200Pb 82 118 199.971827(12) 21.5(4) h β+ 200Tl 0+
201Pb 82 119 200.972885(24) 9.33(3) h EC (99%) 201Tl 5/2−
β+ (1%)
202Pb 82 120 201.972159(9) 5.25(28)×104 y EC (99%) 202Tl 0+
α (1%) 198Hg
203Pb 82 121 202.973391(7) 51.873(9) h EC 203Tl 5/2−
204Pb[n 9] 82 122 203.9730436(13) Observationally Stable[n 10] 0+ 0.014(1) 0.0104–0.0165
205Pb 82 123 204.9744818(13) 1.73(7)×107 y EC 205Tl 5/2−
206Pb[n 9][n 11] Radium G 82 124 205.9744653(13) Observationally Stable[n 12] 0+ 0.241(1) 0.2084–0.2748
207Pb[n 9][n 13] Actinium D 82 125 206.9758969(13) Observationally Stable[n 14] 1/2− 0.221(1) 0.1762–0.2365
208Pb[n 15] Thorium D 82 126 207.9766521(13) Observationally Stable[n 16] 0+ 0.524(1) 0.5128–0.5621
209Pb 82 127 208.9810901(19) 3.253(14) h β 209Bi 9/2+ Trace[n 17]
210Pb Radium D

Radiolead

Radio-lead

82 128 209.9841885(16) 22.3(22) y β (100%) 210Bi 0+ Trace[n 18]
α (1.9×10−6%) 206Hg
211Pb Actinium B 82 129 210.9887370(29) 36.1(2) min β 211Bi 9/2+ Trace[n 19]
212Pb Thorium B 82 130 211.9918975(24) 10.64(1) h β 212Bi 0+ Trace[n 20]
213Pb 82 131 212.996581(8) 10.2(3) min β 213Bi (9/2+)
214Pb Radium B 82 132 213.9998054(26) 26.8(9) min β 214Bi 0+ Trace[n 18]
215Pb 82 133 215.004660(60) 2.34(0.19) min β 215Bi 9/2+#
216Pb 82 134 216.008030(210)# 1.65(0.2) min β 216Bi 0+
217Pb 82 135 217.013140(320)# 20(5) s β 217Bi 9/2+#
218Pb 82 136 218.016590(320)# 15(7) s β 218Bi 0+

Source: Wikipedia

List of Lead Compounds 

Lead makes chemical compounds in two main oxidation states: +2 and +4. This chemical element is present in a vast variety of compounds, such as acetates, chromates, nitrates, oxides, iodides, chlorides, sulfates, etc. 

Despite lead being soluble in water in its elemental form, this chemical property is not always applicable to its compounds. 

The most common compounds of lead include:


  • Lead(II) Nitrate
  • Lead(IV) Nitrate
  • Lead(IV) Phosphate
  • Lead(IV) Carbonate
  • Lead(IV) Sulfate
  • Lead(II) Phosphate
  • Lead(IV) Sulfite
  • Lead(IV) Chloride
  • Lead(II) Chlorate
  • Lead(IV) Chromate
  • Lead(IV) Hydroxide
  • Lead(II) Acetate
  • Lead(IV) Nitrite
  • Lead(II) Oxide
  • Lead(IV) Oxide
  • Lead(II) Dichromate
  • Lead(II) Hydrogen Carbonate
  • Lead(II) Hydrogen Sulfate
  • Lead(II) Sulfate
  • Lead(IV) Bromide
  • Lead(II) Nitride
  • Lead(IV) Dichromate
  • Lead(IV) Cyanide
  • Lead(IV) Iodide
  • Lead(II) Sulfite
  • Lead(II) Nitrite
  • Lead(II) Chromate
  • Lead(IV) Hydrogen Carbonate
  • Lead(II) Cyanide
  • Lead(II) Phosphide
  • Lead(II) Chloride

Lead Carbonate (PbCO3

The lead compound also known as cerussite is a white and highly poisonous chemical. It was once used as a pigment for white paint. Due to its toxicity caused by the lead content, nowadays cerussite has been replaced by the less toxic titanium oxide (TiO2) compound. 

5 Interesting Facts and Explanations

  1. The World Health Organisation (WHO) has classified lead as one of the top 10 substances of utmost public health concern due to its high toxicity which can lead to adverse health effects and death.
  2. One of the routes of lead exposure in young children is the potentially lethal psychological disorder referred to as pica. It’s a disorder that urges children to eat non-edible substances, such as snow, soil, wall paint, chalk, parts of jewelry, etc. All these items may be contaminated with lead which is absorbed into the bloodstream. 
  3. Tobacco smoke presents one of the major and most common causes of indoor air pollution worldwide. In a home where at least one of the residents is a smoker, the facilities must be frequently ventilated. An air purifier is also a good idea. 
  4. The chemical substances contained in tobacco are considered carcinogens according to the United States Cancer Organisation. At least 70 substances of over 4000 chemicals detected in tobacco smoke may lead to some form of cancer. 
  5. In addition to the aforementioned, many of the chemicals contained in tobacco (including the radioactive isotope of lead) are both carcinogens and mutagens, meaning they can both affect genes and trigger the tumorous mutation of cells.