What are lead features?
lead, atomic number 82 in the periodic table, is a metal element with a chemical symbol of PB, which means plumbum , the Latin name of the element. It is a soft, pliable metal that has a silvery-white color when it is freshly cut, but when exposed to air, it quickly gets a matt gray appearance due to the formation of an oxide layer. Although it is sometimes found in its elementary state, the main lead is Galena or lead sulfid (PBS); Other lead ores include Cerussite - lead carbonate (PBCO 3 ) - and anglesite - lead sulphate (PBSO 4 ). Historically, the chemical and physical properties of lead have made a very useful element, but since the end of the 20th century its use has decreased due to its toxicity. However, lead still has a number of important applications-for example in lead batteries, for radiation shielding and as a flexible, durable roof material.
The metal is melted at 622.4 ° F (328 ° C) and boiled at 3 164 ° F (1,740 ° C). Four stable lead isotopes are the end products of the decayVarious naturally occurring radioactive elements such as uranium and thorium through a number of steps. Lead is the heaviest stable element, the resolution that previously belonged to the bismuth - element number 83 - until it was found to be very slightly radioactive. One of the most important physical properties of lead is its ability to absorb high -frequency electromagnetic radiation, such as X -rays and gamma rays. This is due to the high density and a large number of electrons in the lead atom.
lead belongs to the same group as carbon, silicon, germanium and tin. These elements become a more metal character with increasing atomic weight, and while the chemical properties of lead bear some similarity to the other members of the group, it is chemically the most similar to The metal, tin. In its compounds, lead usually has an oxidation state of +2, which means that it dedicates two electrons to other atoms or molecules. Less commonly may have an oxidation state of +4.
metal combines with oxygento form several oxides. "Red lead," formed by a heating lead in the air, has a formula of PB 3 o 4 , but is considered to be a lead oxide compound and lead oxide (PBO 2 ). Lead oxide, also known as litharge, is formed when the metal is strongly heated in the air and can take the form of yellow powder or red crystalline material.
"White lead" is a base carbonate of lead (2PBCO 3 · PB (OH) 2 ). Previously, it was widely used in colors because of its strong white color before it was largely replaced by a non -toxic titanium oxide. In addition to his toxicity, the problem with the white lead was that it tended to respond slowly with sulphide traces (H 2 s) in the air to form a black lead sulfide. This good test for H 2 s, but it meant that old images would darken over time.
lead is most resistant to corrosion of acids because most lead salts have small or no small or nosolubility and form a layer that protects lead from further action. However, it will respond with acetic and nitric acid, because salts created by these reactions - octate and lead nitrates - are very soluble. Lead reacts with "hard" water to create insoluble basic carbonate lead, but creates soluble compounds with soft water, which means that the pipe of lead water represents more risk of leading in soft water.
Probably the most famous lead features is its toxicity. Cases of acute lead poisoning are rare, but it is a cumulative poison and a chronic exposure to a low lead level can lead to a number of serious symptoms. It deactivates the enzymes that produce hemoglobin, leading to the accumulation of preliminary chemical-to the intestine, resulting in constipation and abdominal pain and cause fluid accumulation in the brain, causing headaches. For a long time, this causes anemia and neurological problems.
Chronic lead poisoning was a challengeThey will have a problem due to the widespread use of lead in applications that allowed him to enter the environment. For example, metal lead was previously used in water pipes and lead compounds were used in colors. These uses were interrupted in most countries and the management was replaced by non -toxic alternatives. The biggest source of lead in the environment was the composed tetraethyl lead, which was added to gasoline to achieve smoother combustion. Due to concerns about the health effects of lead in the environment, especially in children in urban areas, there was also gradual gasoline in many countries.