Because not all elements were then known, there were gaps in his periodic table, and Mendeleev successfully used the periodic law to predict properties of some of the missing elements. The first periodic table to become generally accepted was that of the Russian chemist Dmitri Mendeleev in 1869: he formulated the periodic law as a dependence of chemical properties on atomic mass. The underlying reason for these trends is electron configurations of atoms. Trends run through the periodic table, with nonmetallic character (keeping their own electrons) increasing from left to right across a period, and from down to up across a group, and metallic character (surrendering electrons to other atoms) increasing in the opposite direction. Elements from the same column group of the periodic table show similar chemical characteristics. The rows of the table are called periods, and the columns are called groups. The table is divided into four roughly rectangular areas called blocks. It is a graphic formulation of the periodic law, which states that the properties of the chemical elements exhibit a periodic dependence on their atomic numbers. It is widely used in chemistry, physics, and other sciences, and is generally seen as an icon of chemistry. While aquatic plants have a rapid uptake of soluble zirconium, land plants have little tendency to adsorb it, and indeed 70% of plants that have been tested showed no zirconium to be present at all.The periodic table, also known as the periodic table of the ( chemical) elements, is a tabular display of the chemical elements. Zirconium is unlikely to present a hazard to the environment. It is among the long-lived radionuclides that have produced and will continue to produce increased cancers risk for decades and centuries to come. Zirconium 95 is one of the radionuclides involved in atmospheric testing of nuclear weapons. Most passes through the gut without being adsorbed, and that which is adsorbed tends to accumulate slightly more in the skeleton than in tissue. The estimated dietary intake is about 50 microg. Zirconium and its salts generally have low systemic toxicity. Australia, South Africa, India, Sri Lanka and the USA have vast deposits of zircon and zirconia sands. The estimated reserves exceed a billion tonnes. World production is in excess of 900.000 tonnes per year of zircon, and 7000 tonnes of the metal are produced. The chief ores are zircon (ZrSiO4), which is mined in Australia, USA and Sri Lanka, and baddeleyite (Zirconium oxide ZrO2) which is mined in Brasil. Zirconium is more than twice as abundant as copper and zinc and more than 10 times more abundant than lead. Zirconium is not a particularly rare element but because its most common mineral, zircon, is highly resistant to weatering it is only slightly mobile in the environment. The paper and packaging industries are finding that zirconium compounds make good surface coatings because they have excellent water resistance and strength. The metal also has many other uses, among them in photographic flashbulbs and surgical instruments, to make the glass for television, in the removal of residual gases from electronic vacuum tubes, and as a hardening agent in alloys, especially steel. Zircon is also marketed as a natural gemstone used in jewelry. The major end uses of zircon (ZrSiO 4) are refractories, ceramic opacification and foundry sands. Baddeleyite and impure zirconium (zirconia) are used in lab crucibles. Also used in catalytic converters, percussion caps and furnace bricks. Zirconium is used in alloys such as zircaloy, which is used in nuclear applications since it does not readily absorb neutrons. Zirconium does not dissolve in acids and alkalis. Zirconium powder is black and is regarded as very dangerous fire hazard. When it is finely divided, the metal can spontaneously ignite in air, especially at high temperatures. Zirconium is lighter than steel and its hardness is similar to copper. Zirconium is extremely resistant to heat and corrosion. Its chemical and physical properties are similar to those of titanium. Zirconium is a very strong, malleable, ductile, lustrous silver-gray metal. Zirconium - Zr Chemical properties of zirconium - Health effects of zirconium - Environmental effects of zirconium
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