Namrata Das Exams Prep Master
Exams Prep Master
Lead (from the Latin plumbum) is a chemical element with the atomic number 82 and the symbol Pb. It's a type of heavy metal that's denser than most other materials. Lead is soft and pliable, and its melting point is quite low. Lead is silvery with a trace of the blue when freshly cut; when exposed to air, it tarnishes to a drab grey tint. Lead has the highest atomic number of any stable element, and three of its isotopes are nuclear decay endpoints for heavier elements. Here we will discuss lead in detail along with some important questions.
Also check: IUPAC Nomenclature of Organic Compounds
| Table of Contents |
Key takeaways: lead, corrosion-resistant, white lustrous metal, lead monoxide, hydrogen ions.
What is Lead?
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Lead symbol Pb, is a soft metal. It is silverish-white or grey in color. Lead is a poor conductor of electricity and is exceedingly malleable, ductile, and dense. It is highly toxic. Lead (Pb) has been utilized by humans for thousands of years, dating back to 7000 BC. As seen by the continued usage of lead water pipes established by the ancient Romans, lead is extremely robust and corrosion-resistant. Pb is an acronym of the Latin word ‘plumbum’, which means "lead." The element is found in trace amounts in a variety of minerals, with the exception of sulphide and lead glance (PBS), which are used to make the metal all over the world.
Lead
Distribution and Occurrence of Lead
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The late 1700s saw the exploitation of deposits in the Missouri-Kansas-Oklahoma region of the United States, which led to modern advancements. Early biblical accounts frequently mention lead. The Babylonians utilized metal to record inscriptions on plates. At least as early as 200 BCE, the compound known as the white lead was apparently created as a decorative pigment.
Although lead is scarce, natural concentration processes have resulted in significant commercial deposits, primarily in the United States, but also in Canada, Australia, Spain, Germany, Africa, and South America. The western states and the Mississippi Valley in the United States have significant deposits. Lead is present in various minerals but is rarely found free in nature, with the exception of the sulphide, PbS.
Also check: Classification of Haloalkanes and Haloarenes
Uses of Lead
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The ductility, ease of welding, low melting point, high density, and capacity to absorb gamma and X-radiation are all properties that contribute to the diverse applications of elemental lead. For elemental silver and gold, molten lead is an excellent solvent and collector. The poor tensile and fatigue strengths of lead, as well as its tendency to flow even when lightly loaded, limit its structural applications.
Although hydrogen ions can oxidize elemental lead to the Pb2+ ion, the insolubility of most Pb2+ compounds makes lead resistant to many acids. The production of the soluble species of lead in the +2 oxidation state makes oxidation under alkaline conditions easier to achieve. In acidic solution, lead oxide (PbO2, with lead as the Pb4+ ion) is one of the most powerful oxidizing agents, although it is very weak in alkaline solution.
Lead has numerous other uses, the most important of which is the fabrication of storage batteries. Lead is utilized as a protective shielding around nuclear reactors, particle accelerators, X-ray equipment, and containers used to transport and store radioactive materials because it effectively absorbs electromagnetic radiation of short wavelengths.
Read more: Halogenation
Properties of Lead
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Lead and its compounds are toxic and are absorbed by the body, accumulating over time until a deadly dose is reached (a phenomenon known as cumulative poisoning). Lead compounds become more hazardous as their solubility increases. Lead poisoning in youngsters can cause cognitive problems, while it can cause progressive kidney failure in adults. Abdominal pain and diarrhea are the first signs of lead poisoning, followed by constipation, nausea, vomiting, dizziness, headache, and overall weakness. A cure is usually achieved by removing all contact with a lead source. The use of respirators and other protective gear in regions of exposure, as well as the eradication of lead from pesticides and paint pigments, has significantly reduced lead poisoning.
Chemical Properties of Lead
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| Type | Classification | Type | Classification |
|---|---|---|---|
| Group | 14 | Melting point | 327.462°C, 621.432°F, 600.612 K |
| Period | 6 | Boiling point | 1749°C, 3180°F, 2022 K |
| Block | p | Density (g cm−3) | 11.3 |
| Atomic number | 82 | Relative atomic mass | 207.2 |
| State at 20°C | Solid | Key isotopes | 208Pb |
| Electron configuration | [Xe] 4f14 5d10 6s2 6p2 | CAS number | 7439-92-1 |
Compounds of Lead
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Lead compounds have oxidation states of +2 and +4. The oxides: lead monoxide, PbO, in which lead is in the +2 state; lead dioxide, PbO2, in which lead is in the +4 state; and tri-lead tetroxide, Pb3O4 are among the numerous significant lead compounds. Litharge and massicot are two different types of lead monoxide. Litharge, also known as alpha lead monoxide, is a red or reddish yellow solid with a tetragonal crystal structure that is stable below 488 °C (910 °F). Massicot, also known as beta lead monoxide, is a yellow solid with an orthorhombic crystal structure that is stable above 488 degrees Celsius. Both forms are insoluble in water, but they dissolve in acids to create Pb2+ salts.
PbO2 is commercially generated from tri-lead tetroxide by oxidation with chlorine, and it is found in nature as the brown-to-black mineral plattnerite. When heated, it decomposes into oxygen and lesser lead oxides. PbO2 is used as a curing agent for polysulfide rubbers and as an oxidising agent in dyestuffs, chemicals, pyrotechnics, and matches. PbO is further oxidized to generate trilead tetroxide (also known as red lead or minium). It's an orange-red to the brick-red pigment that's typically used in corrosion-resistant paints for exposed iron and steel. It also forms ferrite, which is used to make permanent magnets, when it combines with ferric oxide.
The trihydrate form, Pb(C2H3O2)2H2O, often known as sugar of lead, is used as a mordant in dyeing and as a drier in some paintings. It's also used in the manufacture of various lead compounds and gold cyanidation facilities, where it's used to precipitate soluble sulphides from solution as PbS.
Other salts, such as basic lead carbonate, basic lead sulphate, and basic lead silicate, were once commonly used as white exterior paint pigments. However, since the mid-twentieth century, the usage of so-called white lead pigments has declined significantly due to concerns about their toxicity and health risks. For the same reason, lead arsenate has been virtually phased out of insecticides.
Things To Remember
- Lead symbol Pb, is a soft metal. It is silverish-white or grey in color. Lead is a poor conductor of electricity and is exceedingly malleable, ductile, and dense.
- It is primarily found in the United States, but also in Canada, Australia, Spain, Germany, Africa, and South America.
- Lead compounds have oxidation states of +2 and +4.
- Lead and its compounds are toxic and are absorbed by the body, accumulating over time until a deadly dose is reached.
Sample Questions
Ques. How is Lead important to Humans? (3 marks)
- The metal element is toxic to humans and would attack important internal organs, causing lead poisoning in numerous situations.
- Organ and brain growth in early childhood are reported to be hampered by the metal.
- Lead is one of only a few elements that have been known to humans from ancient times, hence it was never properly discovered. Lead was considered one of the oldest metals by alchemists.
Ques. Why is lead used in the ceramic industry? (2 marks)
Ans. Lead is a soft metal and is metallic greyish due to its lustrous property, it is widely used in ceramic industries to provide lustre and provides the ceramics with a glass-like attractive and decorative look. It is found in pottery glazes as lead bisilicate. If heated for long, it might lead to lead poisoning.
Ques. How to Check Ceramic Clay Pots for Lead Paint? (2 marks)
Ans. Clean the painted or glazed surface to be tested and remove all dust and grime. Crush the two indicated ends of the swab stick with your fingers to activate the test swab. To mix the testing chemicals inside, shake the bottle a few times. Squeeze the swab gently to moisten the swab tip with the liquid testing agent.
Ques. How is Lead Dioxide commercially generated? (2 marks)
Ans. PbO2 is commercially generated from tri-lead tetroxide by oxidation with chlorine, and it is found in nature as the brown-to-black mineral plattnerite. When heated, it decomposes into oxygen and lesser lead oxides. PbO2 is used as a curing agent for polysulfide rubbers and as an oxidising agent in dyestuffs, chemicals, pyrotechnics, and matches.
Ques. What is Lead Poisoning? (2 marks)
Ans. Lead poisoning, also known as plumbism or saturnism, is a form of metal poisoning caused by the presence of lead in the body. The brain is the most delicate organ. Abdominal pain, constipation, headaches, irritability, memory issues, infertility, and tingling in the hands and feet are all possible symptoms. It is responsible for nearly 10% of intellectual disabilities caused by unknown reasons and might lead to behavioral issues.
Ques. What are the uses of Lead? (4 marks)
Ans.
- It's a corrosion-resistant metal that's been used in paints and pipes since the Roman era.
- It's a key component in vehicle batteries and lead-acid batteries.
- For soldering electrical equipment parts.
- In electrolysis procedures, as electrodes.
Ques. How is Lead hazardous? (2 marks)
Ans. Lead poisoning in children can cause cognitive impairments, while in adults it can lead to kidney failure. Constipation, nausea, vomiting, dizziness, headache, and overall weakness are the early indicators of lead poisoning, followed by abdominal discomfort and diarrhea.
Ques. What are the Oxidation states of Lead? (2 marks)
Ans. Lead compounds have oxidation states of +2 and +4. The oxides: lead monoxide, PbO, in which lead is in the +2 state; lead dioxide, PbO2, in which lead is in the +4 state; and tri-lead tetroxide, Pb3O4 are among the numerous significant lead compounds.
Ques. What is ‘sugar of lead’ and what is it used for? (2 marks)
Ans. The trihydrate form, Pb(C2H3O2)2H2O, often known as sugar of lead, is used as a mordant in dyeing and as a drier in some paintings. It's also used in the manufacture of various lead compounds and gold cyanidation facilities, where it's used to precipitate soluble sulphides from solution as PbS.
Ques. How was Lead used in Roman times? (3 marks)
Ans. Basic lead carbonate, basic lead sulphate, and basic lead silicate, were once commonly used as white exterior paint pigments. However, since the mid-twentieth century, the usage of so-called white lead pigments has declined significantly due to concerns about their toxicity and health risks. For the same reason, lead arsenate has been virtually phased out of insecticides
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