Science / Periodic Table of Elements / Lead (Pb): Atomic number: 82, Atomic mass: 207.2 g.mol -1, Electronegativity: 1.8, Density: 11.34 g.cm-3 at 20Â°C, Melting point: 327 Â°C, Boiling point: 1755 Â°C, Vanderwaals radius: 0.154 nm, Ionic radius: 0.132 nm (+2) ; 0.084 nm (+4), Isotopes: 13, Electronic shell: [ Xe ] 4f14 5d10 6s2 6p2, Energy of first ionisation: 715.4 kJ.mol -1, Energy of second ionisation: 1450.0 kJ.mol -1, Energy of third ionisation: 3080.7 kJ.mol -1, Energy of fourth ionisation: 4082.3 kJ.mol -1, Energy of fifth ionisation: 6608 kJ.mol -1, Discovered by: The ancients. Lead is a bluish-white lustrous metal. It is very soft, highly malleable, ductile, and a relatively poor conductor of electricity. It is very resistant to corrosion but tarnishes upon exposure to air. Lead isotopes are the end products of each of the three series of naturally occurring radioactive elements. Applications: Lead pipes bearing the insignia of Roman emperors, used as drains from the baths, are still in service. Alloys include pewter and solder. Tetraethyl lead (PbEt4) is still used in some grades of petrol (gasoline) but is being phased out on environmental grounds. Lead is a major constituent of the lead-acid battery used extensively in car batteries. It is used as a coloring element in ceramic glazes, as projectiles, in some candles to threat the wick. It is the traditional base metal for organ pipes, and it is used as electrodes in the process of electrolysis. One if its major uses is in the glass of computer and television screens, where it shields the viewer from radiation. Other uses are in sheeting, cables, solders, lead crystal glassware, ammunitions, bearings and as weight in sport equipment. Lead in the environment: Native lead is rare in nature. Currently lead is usually found in ore with zinc, silver and copper and it is extracted together with these metals. The main lead mineral in Galena (PbS) and there are also deposits of cerrussite and anglesite which are mined. Galena is mined in Australia, which produces 19% of the world's new lead, followed by the USA, China, Peru' and Canada. Some is also mined in Mexico and West Germany. World production of new lead is 6 million tonnes a year, and workable reserves total are estimated 85 million tonnes, which is less than 15 year's supply. Lead occurs naturally in the environment. However, most lead concentrations that are found in the environment are a result of human activities. Due to the application of lead in gasoline an unnatural lead-cycle has consisted. In car engines lead is burned, so that lead salts (chlorines, bromines, oxides) will originate. These lead salts enter the environment through the exhausts of cars. The larger particles will drop to the ground immediately and pollute soils or surface waters, the smaller particles will travel long distances through air and remain in the atmosphere. Part of this lead will fall back on earth when it is raining. This lead-cycle caused by human production is much more extended than the natural lead-cycle. It has caused lead pollution to be a worldwide issue.
Lead Verb Synonyms: come or be or go first, excel, surpass, exceed, precede, be ahead (of), outstrip, distance, outrun, outdo
Lead Adjective Synonyms: conduct, escort,her, guide, show the way, pilot, steer
Lead Noun Synonyms: direction, guidance, leadership, precedent, example, model, exemplar, pattern, standard
Entertainment / Music / Leading Note: The seventh note of the scale where there is a strong desire to resolve on the tonic. MORE
Technology / Motorcycle / Leading Shoe: A type of drum brake mechanism. The "leading" brake shoe is applied in the direction of the drum rotation. This can either be a single leading shoe or a double (twin) leading shoe design and refers to MORE