Lead Listen is the chemical element with atomic number 82, symbol Pb. Under standard conditions, the single lead body is a malleable, bluish-gray metal that slowly whitens as it oxidizes. The word lead and the symbol Pb come from the Latin plumbum (lead metal).

Lead belongs to group 14 and to period 6 of the periodic table. It is the heaviest with stable elementsb.

Lead is a toxic, mutagenic, and reprotoxic element8, with no known trace element value. It was indeed classified as potentially carcinogenic in 1980, classified in group 2B by the International Agency for Research on Cancer (IARC) 9 then as probably carcinogenic for humans and animals in 20049,10. Two lead salts, chromate and arsenate, are considered to be certain carcinogens by IARC9.

Lead is an environmental contaminant, toxic and ecotoxic from low doses11. The diseases and symptoms it causes in humans or animals are grouped under the name "lead poisoning

Lead - relatively abundant in the earth's crust - is one of the most ancient metals known and worked. They have been found in pigments covering prehistoric tombs or spoils (40,000 years BC), but also objects.

Despite its high toxicity, and probably due to its ease of extraction, its great malleability and its low melting point, it was frequently used during the Bronze Age, hardened by antimony and arsenic found at the same mining sites. It is mentioned in the Sumerian cuneiform scriptures - under the term a-gar512 - almost 5,000 years ago, or in the Exodus, written about 2,500 years ago. It is often also a by-product of silver mining.

Throughout the ages, many writings relate its presence in objects or across cultures. The Sumerians, Egyptians, Greeks, Hebrews and even Romans knew how to extract it. They used it to color and enamel ceramics, to weight hooks, to seal amphorae, to make eyeshadows, to kohl or to produce everyday objects (from 4,000 to 2,000 years before our era). Lead pipes are also found on ancient Roman sites.

In the Middle Ages, alchemists believed that lead was the oldest (and coldest) metal and associated it with the planet Saturn. This is why lead poisoning is called lead poisoning13.

Its toxicity was known to doctors and miners (slaves and prisoners often) of antiquity. The Romans used it in the form of lead acetate to store and sweeten their wine, and had realized that heavy drinkers, therefore of the aristocratic class, suffered from intoxication.

Later, specific symptoms were described, associated with trades such as miners, founders, painters or craftsmen making stained glass.

The death of a child in Australia at the end of the 19th century, after lead poisoning, was the first to raise awareness in a government. It is following the study of many cases of intoxication that regulation, recommendations and screening have gradually been implemented in rich countries (such as Europe or the United States). Lead was thus prohibited for the manufacture of drinking water distribution pipes in Switzerland from 191414 but much later in other countries (example: lead paints were prohibited in 1948 in France but the total ban for pipes only dates from 199515).

Lead has 38 known isotopes, with a mass number ranging from 178 to 215, as well as 46 nuclear isomers. Four of these isotopes, 204Pb, 206Pb, 207Pb and 208Pb, are stable, or at least have been observed stable so far, since they are all suspected of disintegrating by decay into corresponding mercury isotopes, with half extremely long lives16 (which would even be greater than the theoretical half-life of its constituents, the nucleonsc, going beyond 10100 years17'd).

Lead 204 is entirely a primordial nuclide and not radiogenic. The isotopes lead 206, lead 207, and lead 208 are the end products of three decay chains, respectively the chain of uranium (or radium, 4n + 2), actinium (4n + 3) and thorium (4n + 0). Each of these last three isotopes is also, and above all, a primordial nuclide, produced by supernovae as well as by collisions of neutron stars.
The relative amount of radiogenic lead to total lead would be less than 1%.

The four stable isotopes, 204Pb, 206Pb, 207Pb and 208Pb, are present in nature in a ratio 1.4 / 24.1 / 22.1 / 52.4 and 5 radioisotopes are also present in trace amounts. The standard atomic mass of lead is 207.2 (1) u.

Isotopes are sometimes used for isotopic tracing of lead and during isotopic analyzes intended to study the environmental kinetics of certain pollutants in the environment (ex: hunting lead after having been dissolved in the blood of an animal suffering from lead poisoning , industrial fallout lead, or tetraethyl lead from gasoline ...) 18.


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