Wood pencils have never actually contained lead, even though lead is soft enough it could be used for writing.They called tin "plumbum candidum", which means "bright lead". The ancient Romans referred to lead as "plumbum nigrum", which means "black lead". So, for a long time the two elements were considered to be different forms of the same metal. While modern scientists can readily distinguish most elements, it used to be difficult to tell lead and tin apart because the two metals share so many similar properties.In other words, when an electrical current is passed through a sample of lead, heat is neither absorbed nor released. Lead is the only metal which exhibits zero Thomson effect.Unlike many toxins, there really is no safe exposure level to lead, even though it is present in many common materials. It is particularly dangerous to babies and children, where lead exposure can stunt development. The element primarily affects the central nervous system. Lead is found in the mineral galena (PbS) and ores of copper, zinc, and silver. While lead does occur (rarely) in nature in its pure form, most of the lead produced today comes from recycled batteries.
Alchemists associated the metal with the planet Saturn and quested for a way to transmute lead into gold. It is sometimes called the first metal (although the ancients also knew gold silver, and other metals). Lead is one of the metals that was known to ancient man.For example, the metal has a low melting point (327.46 oC) and is a poor conductor of electricity. While lead is dense, ductile, and malleable like many other metals, several of its properties are not what one would consider "metallic". It is a shiny blue-white metal when freshly cut, but oxidizes to a dull gray in air. Lead is a considered a basic metal or post-transition metal.The element name "lead" comes from the Anglo-Saxon word for the metal. Its chemical symbol is Pb, which is based on the word "plumbum", the old Latin name for lead. Natural lead consists of a mixture of 4 stable isotopes, although radioisotopes also exist. This is the highest atomic number for the stable elements. Lead has atomic number 82, which means each lead atom has 82 protons.Oxidation State: The most common oxidation state is 2+, followed by 4+.Appearance: Lead is a metallic gray solid at room temperature.Element Category: Basic Metal or Post-Transition Metal.
0 kommentar(er)
