The Loaded Element Lead

Introduction to Lead

Despite being a soft and malleable metal, the element lead of the periodic table is one of the densest common materials. It’s a silvery blue post-transition metal that turns a dull gray when exposed to air. Construction, batteries, bullets, and leaded gasoline use lead. Lead is the stable element with the highest atomic number on the periodic table: 82.

Ten Interesting & Fun Facts About Lead

Pencils have never used lead. They originally were a tool of wrapped graphite called plumbago, meaning “lead mockup”.
Lead’s symbol, Pb, comes from its Latin name, plumbum. This word referred to most soft metals. Plumbum is also the root of the English word, plumbing.
The Ancient Chinese used lead as a dangerous contraceptive. People who drank lead as a contraceptive often died.
Many used to think that the Roman Empire fell due to lead poisoning. That is likely not true, but lead poisoning was still a major health concern. Recent studies show that ancient Rome’s tap water had about 100 times more lead than today’s spring water.
Venus’s snow is made up of lead sulfide and bismuth sulfide.
In 1993, over 500 tons of lead were added to the Leaning Tower of Pisa to stabilize it. This straightened the tower slightly.
Venetian ceruse was a skin whitener made up of white lead from Venice likely used by Elizabeth I of England. This and other toxic cosmetics may have led to her death.
Lead is one of the most common materials used in radiation shielding. Its density makes it effective in shielding from x-rays and gamma rays.
Most heavier atoms decay into lead, resulting in the amount of lead in the universe gradually increasing over time. In the last 4.5 billion years, the amount of lead increased by .75%. This process of radioactive decay also produces radioactive particles.
Currently, there are over 2 billion tons of lead available, and 88 million tons of lead that can be extracted from reserves.

Lead in the Periodic Table

Lead, atomic symbol Pb, has an atomic number of 82. It lies in group 14 on the periodic table, below tin and to the left of bismuth. This element is the heaviest of the Carbon group, and it has four valence electrons. This makes it less reactive because it would require more energy to lose or gain four electrons.

Lead has an electronegativity of 2.33 (Pauling Scale). Lead’s electron configuration is [Xe] 4f14 5d10 6s2 6p2. Other elements in the carbon family include carbon, silicon, germanium, tin, and flerovium.

Lead Poisoning

Lead is a neurotoxin that can damage the nervous system. It affects every organ and body system when ingested. For more information, visit the Mayo Clinic’s page on lead poisoning.

How Does Lead Poisoning Work?

Lead poisoning damages the nervous system and interferes with enzymes by binding to sulfhydryl groups and mimicking other metals vital to reactions such as calcium, iron, and zinc. Calcium and iron levels can impact the effects of lead, providing protection when high and leading to susceptibility when low.

How Does Lead Poisoning Affect People?

When lead mimics calcium, it can cross the blood-brain barrier and impact the brain. Common neurological effects include impaired memory and focus, mood disorders, headaches, delirium, irritability, and other cognitive deficits. Other common symptoms include high blood pressure, muscle pain, and abdominal pain. Lead poisoning can also affect pregnancy and cause miscarriage, stillbirth, premature birth, lower birth weights, and developmental delays.

How Does Lead Poisoning Happen?

Lead can enter the body through inhalation, ingestion, and skin absorption. The body absorbs nearly all ingested lead and absorbs 20-70% of ingested lead. People working with lead mining, battery manufacturing, and lead recycling. Cigarette smoke also contains radioactive lead-210.

The most common form of lead poisoning comes from contaminated food or water. Crops can become contaminated by soil that accumulated lead from pipes and residual emissions. Lead water pipes can dissolve when exposed to soft or acidic water and cause health problems. Hard water creates a protective layer of lead carbonate and lead sulfate preventing lead from dissolving.

Children absorb more lead when exposed. Lead-based paint is the largest source of exposure for children. Paint deteriorates and creates dust that can enter the body. Chewing on old window sills covered in lead paint is a direct source of lead poisoning. Some plastic toys also expose children to lead. Plastic containing lead is more flexible and stable from heat.

Lead in the Roman Empire

The Roman Empire relied heavily on lead. They beat it into sheets used for plumbing and other piping. Cooking pots and utensils lined with lead prevented the taste of copper from contaminating the food. Lead was used as a wine sweetener. This led to the common disease known as “saturnine gout,” now known as a form of lead poisoning. The Romans mined 80,000 tons of lead per year, a high in lead production not reached again until the Industrial Revolution. The Romans actually knew about the toxicity of lead but continued to rely on it anyway.

Environmental Concerns

Lead is being phased out from many uses including solders and water systems due to environmental concerns. Lead can accumulate in the soil where it can compete with other metals to disrupt photosynthesis in plants. Contaminated soil can also cause lead to travel the food chain and affect other animals. Additionally, fish can absorb lead from contaminated water and sediment. Fishing sinkers contaminate seawater. The United States banned lead sinkers for a month in 2017 before the band became ineffective. Spectrophotometry, x-ray fluorescence, and electrochemical techniques can determine lead levels in the environment.

Lead Applications in Today’s World

What is Lead Used for?

Batteries and bullets are the main sources of lead today. Cosmetics, paint, and other materials no longer contain lead due to toxicity concerns. Scuba diving weight belts, organ pipes, x-ray shielding, and ballast in sailboat keels, contain lead. In addition, candlewick treatment that extends burn time uses lead.

Bullets

Lead is the main metal used for bullets, and has been since the invention of the bullet. Additionally, it is inexpensive, requires minimal equipment, and has better velocity retention due to its density. Lead also has less rebound and is cast at low temperatures.

Construction

Lead is easy to extract and work with, so it is commonly used for construction. Acoustic dampeners, wire casing, pipes, stained glass, plumbing, sculptures, roofing, and gutters contain lead. Lead paint prevents corrosion of iron and steel structures such as bridges and railways.

Batteries

Batteries contain both elemental lead and lead compounds. This is the most common modern use of lead. Lead, lead dioxide, and sulfuric acid react within batteries to create a voltage source. This is less of a toxicity concern since there is no direct contact between the lead in batteries and humans. Supercapacitors in Australia, Japan, and the United States use lead. Lead batteries have lower energy density but are much cheaper than lithium-ion batteries.

Where is Lead Found?

Lead is rare in its metallic form and is often found in the mineral galena combined with zinc ores. It is classified as a chalcophile because it is often found with sulfur. Lead is the 38th most abundant element in Earth’s crust with a crustal abundance of 14 ppm. China produces nearly 50% of all lead. Australia, Peru, and the United States also mine lead.

When and How Was Lead Discovered?

The first found example of lead smelting dates back to 7000-6500 BCE in Asia Minor. When first discovered, it had few applications. The Ancient Egyptians were the first to widely use lead for purposes such as cosmetics, fishing nets, and pottery. The Ancient Chinese used lead as a currency. The production of lead was the biggest during the Industrial Revolution.

Lead Chemistry- Compounds, Reactions, Oxidation States, Isolation

Chemical Properties of Lead Element

When exposed to air, lead reacts to form a layer mostly comprised of Lead (II) carbonate making the lead chemically inert. At room temperature, fluorine reacts with lead, but chlorine requires heat for a reaction to take place. Lead doesn’t react with sulfuric or phosphoric acid but can be impacted by hydrochloric and nitric acids.

Lead Compounds

The element lead often forms covalent compounds rather than metallic alloys. Here are a few common lead compounds and their uses:

Lead (II, IV) Oxide

Referred to as “red lead,” this compound has a bright red/orange color used for pigments. Its molecular formula is Pb₃O₄. It’s also used in batteries and primer paint. It is a mixed-valence compound, with Pb(II) and Pb(IV) found in a ratio of 2:1.

Lead Monoxide

This compound (PbO) is a pale yellow color. This is the lead compound used most often in glass. It is also used in ceramics to make the material more inert.

Lead Dioxide

This dark brown compound (PbO₂) is insoluble in water and valuable to electrochemistry. Matches and pyrotechnics as well as dyes use lead dioxide.

Lead Sulfate

Lead sulfate (PbSO₄) is a minimally soluble white powder used in electrodes on car batteries. It forms when the battery discharges and transforms into metallic lead and sulfuric acid on the negative terminal and lead dioxide and sulfuric acid on the positive terminal.

Lead (II) Acetate

This compound (Pb(CH₃COO)₂) holds many names including sugar or lead, salt of Saturn, and Goulard’s powder for its sweet taste. It’s soluble and water and has a white crystalline appearance. Hair dyes contain lead (II) acetate in low concentrations. Additionally, lead (II) acetate sweetened wine and was in cosmetics in the Roman Empire. Pope Clement II is the first death on record from lead acetate. Ludwig van Beethoven may have also died from this cause.

Isolation of Lead

Lead is refined from lead ore mostly consisting of galena. This process requires ore concentration, smelting, and refining. Nearly 50% of lead is recycled material and over 90% of lead used in the United States is recycled. Recycling lead is a two-stage process involving smaller furnaces to heat the lead and a carbon-based reducing agent.

Lead Oxidation States

The two main oxidation states of lead are +4 and +2. Compounds are usually in the +2 state with the lighter elements of the carbon group. In solution, lead ions are often colorless.

Physical Properties of Lead

Though lead is denser than other common metals such as iron, copper, and zinc, it is not the densest metal. Tungsten is denser than lead, and osmium is the densest metal with a density almost twice that of lead. On the Mohs scale, Lead has a hardness of 1.5. This means it is soft enough to be scratched with a nail. Lead is somewhat ductile and with low tensile strength. It has a low melting point and the lowest boiling point in the carbon group.

Symbol: Pb
Melting point: 327.46°C
Boiling point: 1749°C
Density (g cm−3): 11.34
Atomic mass: 207.2
Atomic number: 82
Electronegativity (Pauling Scale): 2.33
Classification: Post-transition metal, Group 14 metal
Crustal abundance (ppm): 14
Electron configuration: [Xe] 4f14 5d10 6s2 6p2
Key Isotopes: 204Pb, 206Pb, 207Pb, 208Pb
Found naturally in the minerals: Galena, Boulangerite, Anglesite, Cerussite
Toxicity: High exposure is very toxic and can lead to death

Where Can I Buy Elemental Lead?

Hardware stores such as ACE Hardware and metal websites such as RotoMetals and Metal Shipper sell lead ingots and nuggets in various weights. A kilogram of lead costs about $4-10.