Strontium

Strontium has the atomic symbol Sr and the atomic number 38. It is a soft silver-white or yellowish (when oxidised) metallic element that is even more chemically reactive than its neighbour calcium.

Strontium is a grey, silvery metal that is softer than calcium and even more reactive toward water, with which it reacts on contact to produce strontium hydroxide and hydrogen gas.  Finely powdered strontium metal ignites spontaneously in air at room temperature. Most of us will be familiar with strontium because strontium salts are commonly used in fireworks and flares to give a bright (some might say blinding) red color to flames.

Strontium is named after Strontian, a village in Scotland near which the mineral was first discovered in 1790.  Strontium is the 15th most abundant element on Earth, but because of its reactivity, strontium is not found roaming freely in the wild: it occurs in minerals, mostly in strontianite and celestite.

Because its nucleus is very nearly the same size as that of calcium, the body mistakenly takes up strontium and incorporates it into bones and tooth enamel in the place of calcium. Surprisingly, this is not a health problem and in fact, it can provide a health benefit. For example, in clinical trials, the drug strontium ranelate was found to aid bone growth, increase bone density, and lessen vertebral, peripheral, and hip fractures in women.

The radioactive isotope, ⁹⁰Sr, is common in radioactive fallout. Since radioactive fallout doesn't respect national borders, it falls upon all living things regardless of nationality or species, contaminating water, food and even the air that we all breathe. This isotope is quite dangerous and can cause a variety of leukæmias, bone cancer and other debilitating bone diseases. Perhaps ironically, Strontium-90 is also used to treat cancer.

For more information visit:-
http://www.theguardian.com/science/punctuated-equilibrium/2011/nov/18/1?guni=Article:in%20body%20link
http://en.wikipedia.org/wiki/Strontium

Antimony

Antimony is a chemical element with symbol Sb (from Latin: stibium) and atomic number 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb₂S₃).

 

Antimony compounds have been known since ancient times and were used for cosmetics.  Nowadays Antimony is mainly used as its trioxide in making flame-proofing compounds and in certain alloys.  The Egyptians had a hieroglyph for Antimony......

Antimony has no known biological role, but it is a potent toxin, with effects that are similar to arsenic poisoning. When ingested, antimony strongly bonds to sulfur-containing enzymes, thereby inactivating them. Antimony is even more toxic when inhaled as the gas, stibine, SbH₃. Poisoning by antimony ingestion manifests as gastric distress, and large doses cause vomiting, and kidney and liver damage, followed by death a few days later.

It was thought that Mozart was a victim of poisoning at the hand of rival composer, Antonio Salieri, although historians don't give this hypothesis any credence. It is far more likely that Mozart was poisoned by his doctors. A heavy drinker, Mozart was known to also overindulge in the popular hangover cure of the day that contains antimony, tartar emetic, C₄H₄KO₇Sb, which was provided by his doctors.

Stibnite

For some time, China has been the largest producer of antimony and its compounds, with most production coming from the Xikuangshan Mine in Hunan. The industrial methods to produce antimony are roasting and subsequent carbothermal reduction or direct reduction of stibnite with iron.

For more information visit:-
http://www.theguardian.com/science/grrlscientist/2012/feb/24/1?guni=Article:in%20body%20link
http://en.wikipedia.org/wiki/Antimony

Holmium

Holmium is a chemical element with the symbol Ho and atomic number 67 and is a rare earth element. It was discovered by Swedish chemist Per Theodor Cleve. Its oxide was first isolated from rare earth ores in 1878 and the element was named after the city of Stockholm.

It is a relatively soft and malleable silvery-white metal. It is too reactive to be found uncombined in nature, but when isolated, is relatively stable in dry air at room temperature. However, it reacts with water and rusts readily, and will also burn in air when heated.

Holmium has the highest magnetic strength of any element and therefore is used for the polepieces of the strongest static magnets.

Holmium oxide appears to have different colours depending on changes in ambient lighting. Under natural light, it's yellow, but under fluorescent lighting, it's pink.

Ho₂O₃, left: natural light, right: fluorescent lamp light

Holmium is used in yttrium-iron-garnet (YIG)- and yttrium-lanthanum-fluoride (YLF) solid-state lasers found in microwave equipment (which are in turn found in a variety of medical and dental settings). Holmium lasers emit at 2.08 micrometres, and therefore are safe to eyes^. They are used in medical, dental, and fibre-optical applications.

Holmium is one of the colorants used for cubic zirconia and glass, providing yellow or red colouring.  Glass containing holmium oxide and holmium oxide solutions (usually in perchloric acid) have sharp optical absorption peaks in the spectral range 200–900 nm. They are therefore used as a calibration standard for optical spectrophotometers and are available commercially.

For more information visit:-
http://en.wikipedia.org/wiki/Holmium
http://www.theguardian.com/science/grrlscientist/2012/aug/10/1?guni=Article:in%20body%20link

Cobalt!

Cobalt is a chemical element with symbol Co and atomic number 27. Like nickel, cobalt in the Earth's crust is found only in chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, produced by reductive smelting, is a hard, lustrous, silver-grey metal.

Cobalt-based blue pigments (cobalt blue) have been used since ancient times for jewellery and paints, and to tint glass blue, but the colour was later thought by alchemists to be due to the known metal bismuth. Miners had long used the name kobold ore (German for goblin ore) for some of the blue-pigment producing minerals; they were named because they were poor in known metals, and gave poisonous arsenic-containing fumes upon smelting. In 1735, such ores were found to be reducible to a new metal (the first discovered since ancient times), and this was ultimately named for the kobold.

Cobalt is primarily used as the metal, in the preparation of magnetic, wear-resistant and high-strength alloys. Its compounds cobalt silicate and cobalt(II) aluminate (CoAl₂O₄, cobalt blue) give a distinctive deep blue color to glass, ceramics, inks, paints and varnishes.

Cobalt blue tinted glass

Free cobalt (the native metal) is not found in on Earth, except as recently delivered in meteoric iron (see below). Though the element is of medium abundance, natural compounds of cobalt are numerous. Small amounts of cobalt compounds are found in most rocks, soil, plants, and animals.

Cobalt forms many useful alloys. It is alloyed with iron, nickel, and other metals to form Alnico, an alloy with exceptional magnetic strength. Cobalt, chromium, and tungsten may be alloyed to form Stellite, which is used for high-temperature, high-speed cutting tools and dies. Cobalt is used in magnet steels and stainless steels. It is used in electroplating because of its hardness and resistance to oxidation. Cobalt salts are used to impart permanent brilliant blue colours to glass, pottery, enamels, tiles, and porcelain. Cobalt is used to make Sevre's and Thenard's blue. A cobalt chloride solution is used to make a sympathetic ink. Cobalt is essential for nutrition in many animals. Cobalt-60 is an important gamma source, tracer, and radiotherapeutic agent.



For more information visit:-
http://en.wikipedia.org/wiki/Cobalt
http://www.theguardian.com/science/punctuated-equilibrium/2011/sep/02/1?guni=Article:in%20body%20link

Krypton!!!

Krypton is name of the fictional home planet of Superman currently in the local cinemas as the Man of Steel.

Krypton is a chemical element with symbol Kr and atomic number 36. It is a member of group 18 (noble gases) elements. A colourless, odourless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionally distilling liquified air, and is often used with other rare gases in fluorescent lamps. Krypton is inert for most practical purposes.

Krypton gas discharge tube

Krypton was discovered in Britain in 1898 by Sir William Ramsay, a Scottish chemist, and Morris Travers, an English chemist, in residue left from evaporating nearly all components of liquid air. Neon was discovered by a similar procedure by the same workers just a few weeks later.  William Ramsay was awarded the 1904 Nobel Prize in Chemistry for discovery of a series of noble gases, including krypton.

Krypton is characterized by several sharp emission lines (spectral signatures) the strongest being green and yellow.  It is one of the products of uranium fission.  Solidified krypton is white and crystalline with a face-centered cubic crystal structure, which is a common property of all noble gases (except helium, with a hexagonal close-packed crystal structure).

Kryptonite on the other hand is a fictional form of a radioactive element from Superman's home planet of Krypton. It is famous for being the ultimate natural weakness of Superman and most other Kryptonians, and the word Kryptonite has since become synonymous with an Achilles' heel—the one weakness of an otherwise invulnerable hero.  In the Superman films Kryptonite is green although the original stores there were many colour variations.

Superman's worst nightmare!

Krypton-83 has application in magnetic resonance imaging (MRI) for imaging airways.  Much more useful than the ill effects of Kryptonite!

Uranium!!

Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with symbol U and atomic number 92. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all its isotopes are unstable. The most common isotopes of uranium are uranium-238 (which has 146 neutrons) and uranium-235 (which has 143 neutrons). Its density is about 70% higher than that of lead, but not as dense as gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

Cubes and cuboids of uranium photographed in the 1940s.
Image: U.S. Department of Energy (public domain).

 
Uranium was named after the planet Uranus, which had been discovered eight years prior to the discovery of uranium. Uranus was named in honour of the Greek god of the sky.
 
Uranium is more abundant and widespread than most people realise -- it occurs in low levels in all rock, soil, and water, and is, for example, more abundant than silver. It is the largest element found on Earth in significant quantities. In the wild, nearly all uranium is the uranium-238 (99.27%) isotope, although there are trace amounts of naturally-occurring uranium-235 and even smaller amounts of uranium-234. Uranium is radioactive and decays by emitting alpha particles (two protons and two neutrons bound together). The half-life of uranium-238 is about 4.47 billion years and that of uranium-235 is 704 million years.
 
Before it was discovered that uranium is radioactive, it was widely used to colour glass, and pottery and glazes.
 
The atomic bomb, named "Little Boy", that was dropped on Hiroshima Japan in 1945, contained 64 kg (140 lb) of highly-enriched U-235. This bomb had an explosive energy of 16 kilotonnes of TNT, it killed an estimated 90,000–166,000 people and destroyed roughly 50,000 buildings.
 
After enrichment, the barely radioactive U-238 remains behind. Known as depleted uranium, it is used as shielding for radioactive materials, or as "high-density penetrators" -- which is military talk for dense pointy projectiles that smash holes through otherwise impenetrable objects.

 

Uraninite, also known as pitchblende, is the most common ore mined to extract uranium.

A person can be exposed to uranium (or its radioactive daughters such as radon) by inhaling dust in air or by ingesting contaminated water and food. The amount of uranium in air is usually very small; however, people who work in factories that process phosphate fertilizers, live near government facilities that made or tested nuclear weapons, live or work near a modern battlefield where depleted uranium weapons have been used, or live or work near a coal-fired power plant, facilities that mine or process uranium ore, or enrich uranium for reactor fuel, may have increased exposure to uranium.
 
Houses or structures that are over uranium deposits (either natural or man-made slag deposits) may have an increased incidence of exposure to radon gas.
 
Most ingested uranium is excreted during digestion. Only 0.5% is absorbed when insoluble forms of uranium, such as its oxide, are ingested, whereas absorption of the more soluble uranyl ion can be up to 5%. However, soluble uranium compounds tend to quickly pass through the body whereas insoluble uranium compounds, especially when inhaled by way of dust into the lungs, pose a more serious exposure hazard. After entering the bloodstream, the absorbed uranium tends to bioaccumulate and stay for many years in bone tissue because of uranium's affinity for phosphates. Uranium is not absorbed through the skin, and alpha particles released by uranium cannot penetrate the skin.
 
Incorporated uranium becomes uranyl ions, which accumulate in bone, liver, kidney, and reproductive tissues. Uranium can be decontaminated from steel surfaces and aquifers.

To explore Uranium more visit the excellent articles below:-
http://www.guardian.co.uk/science/grrlscientist/2013/jun/21/1
http://en.wikipedia.org/wiki/Uranium

The Periodic Table

The Periodic Table

A periodic table is a tabular display of the chemical elements, organized on the basis of their atomic numbers, electron configurations, and recurring chemical properties. Elements are presented in order of increasing atomic number (number of protons). The standard form of table comprises an 18 × 7 grid or main body of elements, positioned above a smaller double row of elements. The table can also be deconstructed into four rectangular blocks: the s-block to the left, the p-block to the right, the d-block in the middle, and the f-block below that. The rows of the table are called periods; the columns of the s-, d-, and p-blocks are called groups, with some of these having names such as the halogens or the noble gases. Since, by definition, a periodic table incorporates recurring trends, any such table can be used to derive relationships between the properties of the elements and predict the properties of new, yet to be discovered or synthesized, elements. As a result, a periodic table—whether in the standard form or some other variant—provides a useful framework for analyzing chemical behavior, and such tables are widely used in chemistry and other sciences.

 

Although precursors exist, Dmitri Mendeleev is generally credited with the publication, in 1869, of the first widely recognized periodic table. He developed his table to illustrate periodic trends in the properties of the then-known elements. Mendeleev also predicted some properties of then-unknown elements that would be expected to fill gaps in this table. Most of his predictions were proved correct when the elements in question were subsequently discovered. Mendeleev's periodic table has since been expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour.

 

Download a copy here.

http://en.wikipedia.org/wiki/Periodic_table
http://iupac.org/