O lead it is a metal very versatile for its malleability, ductility, hardness and resistance to oxidation; and yet, a toxic and bioaccumulative metal, considered an environmental contaminant, in addition to being offensive to human health. Lead is currently used in the manufacture of batteries, shielding blankets, cables, gasoline additives, among others.
Read too: Carbon - chemical element that can be found in different ways in nature
Lead properties
Symbol: Pb
Pastaatomic: 207.2 u
Numberatomic: 82
electronegativity: 2.33 (Pauling)
Settingselectronics: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 5d10 4f14 6p2
Serieschemistry: representative metal
PointinFusion: 327.46°C
Pointinboiling: 1748.85 °C
Density: 11,340 kg/m3
Toughness: 1.5 (Mohs scale)
Solubility in water (25°C): 9580 mg/L
Lead Characteristics
lead is a heavy metal, with low hardness, therefore, being easy to handle (soft), it is not a good conductor of electricity. It is an amphoteric element, that is, react in half acid and basic, has corrosion resistance of
hydrochloric acids and sulfuric diluted, but dissolves in nitric acid, and further reacts with the Acetic Acid, not being, therefore, suitable for the manufacture of utensils for culinary use.Under normal conditions of temperature and pressure, lead has solid appearance, bluish gray in color. Lead is also a toxic and bioaccumulative metal, which can cause biochemical and functional changes in living organisms.
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Lead Applications
Lead is widely applied as metal alloys, which, mixed with elements like tin, copper, antimony, arsenic, bismuth, cadmium and sodium, form materials with diverse applications. Organic salts, silicates and carbonates of lead as reagents in chemical processes and additives:
Lead-acid batteries;
Manufacture of power cable linings;
Materials used in construction;
Gasoline additive (tetraethyl lead - Pb (C)2H5)4);
Formulation of pigments for ships (inhibits the fixation of crustaceans);
Radiation shielding blanket;
Stabilizer additives against heat and light, applied in the manufacture of plastics;
Pb lead nitride (N3)2, applied in the manufacture of explosive detonators.
lead poisoning
The effects of lead on the body are independent of the route of absorption, but the main ones are inhalation, especially in the case of occupational exposure, and ingestion of contaminated water and food. O nervous system is most affected by the presence of metal in the body, which can cause encephalopathy, cognitive deficit and damage to motor functions.
the lead can interfere with the blood system, in the synthesis of cells responsible for the transport of oxygen and in endocrine functions; can cause kidney problems; and decrease male fertility. In case of severe poisoning, it causes gastrointestinal damage and can cause constipation, diarrhea and gastritis.
See too: Niobium - metal with various industrial and commercial applications
lead history
The word lead comes from the Latin, plumbum, which explains the symbol for the lead atom being Pb. There are hypotheses that lead has been in use for 7,000,000 years, this is due to the ease of extraction, malleability and ductility of the metal. In the Torah, or in the Hebrew Bible, the book of Exodus mentions the element, citing it as something dense:
“You blew with your wind, the sea covered them; they sank like lead in vehement waters.”
Exodus 15:10
In the British Museum in London, it is kept the oldest piece of lead discovered until then, dates that it was created in 3800 BC. Ç. There are records that the Chinese extracted and manipulated lead in 3000 BC. Ç.; the Phoenicians, in 2000 BC. a., explored the metal.
Today, in Rome, there are lead pipes with the insignia of emperors who reigned in 300 BC. C., as they are even one of the possible causes of dementia for many government officials and their families, as, in addition to the lead that contaminated the water, through the tubes, the Romans used lead acetate to sweeten wines, in addition to lead compounds that were applied in the formulation of cosmetics and paints. The durability of the metal was applied by the Egyptians in the manufacture of weapons, ornaments and utensils.
Obtaining lead
Lead is mainly obtained from of lead II sulfide, found in the mineral galena, which has about 87% lead in its composition. For lead extraction, roasting is carried out, which is the heating of the sulfide in the presence of oxygen gas, obtaining lead oxide as a product, according to the reaction:
The lead oxide obtained is taken to an oven with reducing agents. Lead is separated by distillation and flotation, and the result of this process is metallic lead, with a purity of 99.99%.
Also access: What are the names of the new chemical elements?
solved exercises
Question 1 - (AOCP Institute) For the criminal expert, having knowledge about the periodic table is essential because it allows the identification of a chemical element. Therefore, mark the correct alternative regarding the location of the lead and the respective behavior of the atom.
A) Lead is a chemical element with the symbol Pb, atomic number 82 (82 protons and 82 electrons), with mass atomic equal to 207.2 u, belonging to group 14 or IVA of the periodic classification of elements chemicals. At room temperature, lead is in a solid state.
B) Lead is a chemical element with symbol Pb, atomic number 82 (82 protons and 82 electrons), with mass atomic equal to 207.2 u, belonging to group 12 or VAT of the periodic classification of elements chemicals. At room temperature, lead is in a solid state.
C) Lead is a chemical element with the symbol Pb, atomic number 22 (82 protons and 82 electrons), with mass atomic equal to 207.2 u, belonging to group 11 or VAT of the periodic classification of elements chemicals. At room temperature, lead is in a solid state.
D) Lead is a chemical element with the symbol Pb, atomic number 82 (82 protons and 82 electrons), with mass atomic equal to 107.2 u, belonging to group 12 or IVA of the periodic classification of elements chemicals. At room temperature, lead is in a solid state.
E) Lead is a chemical element with the symbol Pb, atomic number 82 (82 protons and 82 electrons), with mass atomic equal to 227.2 u, belonging to group 13 or IVA of the periodic classification of elements chemicals. At room temperature, lead is in a solid state.
Resolution
Alternative A.
B – Incorrect: The lead does not belong to group 12 of the table, but to 14.
C – Incorrect: The atomic number of lead is not 22, but 82, and its group is not 11.
D – Incorrect: The atomic mass of lead is not 107.2 u, but 207.2 u, and it does not belong to group 12, but to 14.
E – Incorrect: Lead does not have an atomic mass of 227.2 u, but 207.2 u, and its group is also not 13, but 14.
Question 2 - Regarding lead metal, it is incorrect to state that:
A) It is a malleable, ductile, bluish gray colored metal.
B) It is a malleable metal, conductive of electricity, used in the manufacture of wires.
C) It is an easily obtainable metal, with infinite versatility of use, especially in civil construction.
D) Lead was one of the first metals to be manipulated by humans, metal was used as a reference for a dense element in biblical inscriptions.
E) Lead, despite its versatility, is a toxic metal that can cause problems in the nervous, gastric and kidney systems.
Resolution
Alternative B. Lead is a malleable metal and is used in the manufacture of wires, but to cover the conducting wires. Lead itself is not a good conductor of energy.
By Laysa Bernardes Marques de Araújo
Chemistry teacher
