Lead (Pb) Susan Pang
Natural occurrence and Extraction • Natural occurrence Lead is a naturally occurring metal found deep in the ground. It occurs in small amounts in ore, along with other elements such as silver, zinc or copper. It exists in its native form, though it is rarely found uncombined, and is more likely obtained from a mineral called galena. • Extraction The ore is concentrated by the flotation process and is then refined by electrolysis or by smelting.
Reactions • Lead is generally unreactive • It does not react with water under normal conditions • Only reacts with oxygen when heated strongly to melt into a silvery ball and forms a powder • Reacts very slowly with cold, dilute acids, and only reacts with certain acids
Physical Properties • Bluish-white • Tarnishes to dull gray in the air • Highly malleable and ductile (can be shaped or bent) • Poor conductor of electricity and heat • Extremely resistant to corrosion • Relatively soft • Is toxic
Chemical Properties • Atomic number - 82 • Atomic mass - 207.2 g/mol -1 • Density - 11.34 g/cm-3 at 20°C • Melting point- 327°C • Boiling point -1755°C • Isotopes- 13
Who discovered it? • It is unknown how lead was discovered or who discovered it because it was so long ago, and when it was discovered no records were kept. • However lead has been known and used since ancient times, dating back to almost 7000 years ago. • It has been mentioned in the Bible • It has been found in archaeological dig sites from over 5000 years ago, which means people knew how to refine it even before the pyramids in Egypt were built. • The ancient Romans used it to make water pipes, which are still used today.
Ancient Uses • People in ancient times used lead for • Glassware • In architecture and engineering • In writing utensils • Pots and vases • Food and cosmetics • Water pipes and plumbing • Unfortunately for the ancient people, lead is a cumulative poison and causes lead poisoning if ingested. Their lack of scientific techniques made a lot of them unable to realise the dangers of lead, and a lot of them died as a result.
Modern Uses • Lead is important as it is used to develop and create a variety of things we use today: • Storage batteries • Pipes • Shielding from radiation (e.g x-ray machines and nuclear reactors) • Covering on wires and cables to protect from corrosion • Ammunition • Ceramics • Paints and insecticides
Lead today • Major producers Galena is mined in Australia, which produces 19% of the world’s lead supply, followed by the USA, China, Peru and Canada. Some of it is also mined in Mexico and the west of Germany. • How has lead affected population When the mining of lead is not carefully done, the air, soil and vegetation can all be contaminated by it, affecting the population of people living close to the mines. Their healths will decline and their blood levels will have dangerously high amounts of lead present, which may lead to lead poisoning and cause many nasty ailments.
Environmental Impact • Lead can end up in the water and soil through corroded lead pipelines and through corrosion of leaded paints. It cannot be broken down, only converted to other forms. • Lead can accumulate in the bodies of aquatic and soil organisms, causing their health to be affected from lead poisoning. Health effects in aquatic animals can take place even if there are very small concentrations present. • The bodily functions of phytoplankton can be disturbed by lead. Phytoplankton is an important source of oxygen production in seas and many larger sea-animals eat it. This could affect the balance of the food chain. • The functions of soil are disturbed by the presence of lead, especially near highways and farmlands, where extreme concentrations may be present. Organisms in the soil then suffer from lead poisoning too. • Lead is a particularly dangerous element, as it can accumulate not only in individual organisms, but also in entire food chains.
Health Issues • Lead is one of the four metals that have the most damaging effects on human health. • Lead poisoning occurs when lead builds up in the body over a period of time • Even small amounts can cause serious health problems, and in high levels, it can be fatal • Small children are especially vulnerable to lead poisoning • Lead poisoning can affect the brain, nervous system, blood cells and kidneys • It can cause: • A rise in blood pressure • Kidney damage • Miscarriages and abortions • Disruption of nervous systems • Brain damage • Decreased IQ and learning abilities in children • Behavioural disruptions in children
Sources • Bregante, M. (n.d.). Use and misuse of lead. Use and misuse of lead. Retrieved from http://www.phyles.ge.cnr.it/htmling/useandmisuseoflead.html • Helmenstine, A. (n.d.). Lead Facts. About.com. Retrieved from http://chemistry.about.com/od/elementfacts/a/lead.htm • Lead. (n.d.). Infoplease. Retrieved from http://www.infoplease.com/encyclopedia/science/lead-chemical-element-natural-occurrence-processing.html • Lead. (2013, September 9). National Institute of Environmental Health Sciences. Retrieved from http://www.niehs.nih.gov/health/topics/agents/lead/ • Lead Element Facts. (n.d.). Chemicool. Retrieved from http://www.chemicool.com/elements/lead.html • Lead - Pb. (n.d.). Water Treatment and Purification - Lenntech. Retrieved from http://www.lenntech.com/periodic/elements/pb.htm • Who Discovered Lead?. (n.d.). Who Discovered It?. Retrieved from http://discovery.yukozimo.com/who-discovered-lead/