As of 1700, only seven of the 84 metal elements on the periodic table were identified. These “Metals of Antiquity” were gold, copper, silver, lead, tin, iron and mercury.
Every element on the periodic table has its own atomic number, atomic weight and chemical symbol. Lead, for example, has an atomic number of 82, which means there are 82 protons in every atom. Its atomic weight (or relative atomic mass) is 207.2, which is the ratio of the average mass of an atom of lead compared to 1/12th of the mass of an atom of a carbon-12 isotope. Lead’s chemical symbol is Pb. It derives from the Latin word plumbum, which means “liquid silver”.
Half-life is the measure of how long it takes an unstable element to decay. A half-life of one day means that it would take that time for half the atomic nuclei in a sample to decay into a more stable element. In 2003, French scientists discovered that bismuth-209, previously believed to be radioactively stable, in fact gradually decays with a half-life of around 20 billion billion years -more than a billion times the age of the universe.
Technetium (Tc) was discovered in 1937 by Carlo Perrier and Emilio Segre (both ITA) at the University of Palermo in Sicily, Italy.
They isolated the element from a sample of molybdenum (Mo), which had been exposed to high levels of radiation in a particle accelerator known as a cyclotron. Its most stable isotope, technetium-98, has a half-life of around
4.2 million years, meaning that any significant mineral deposits in the Earth’s crust have long since radioactively decayed into ruthenium-98.
In Dec 2002, scientists at the State University of New York, USA, managed to create francium (Fr) atoms using a heavy ion nuclear fusion reactor, collecting more than 300,000 together in a magneto-optical trap. Francium’s most stable isotope has a half-life of just 22 min, making it the most unstable naturally occurring element. It has no practical uses.
As of 2016, the UK held around 126 tonnes (277,782 lb) of plutonium (Pu), 23 tonnes (50,706 lb) of which is owned by other nations.
A by-product of uranium used in nuclear reactors, the plutonium is stored at the Sellafield nuclear site in Cumbria. It exists in powdered form and is kept
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Naturally occurring element
In 1971, US scientist Darleane Hoffman published her discovery of small amounts of plutonium-244 in Precambrian phosphate deposits found in California, USA. Plutonium has an atomic number of 94.
Occupying group 1, or the left-most column of the periodic table, alkali metals are soft and highly reactive, with low density. Although caesium’s atomic number of 55 is lower than that of francium (87), francium is only visible in microscopic amounts in the Earth’s crust and is invisible to the naked eye.
The lanthanide metals consist of the 15 elements with atomic numbers 57 to 71 and are sometimes known as the “rare earth elements”, along with yttrium and scandium. Lutetium’s atomic number of 71 makes it the heaviest of the group.
All elements in groups 3-12 of the periodic table (with the exception of lutetium and lawrencium) are known as transition metals. Less reactive than alkali metals, transition metals are good conductors of heat and electricity and include gold, copper and iron. With an atomic number of 112, copernicium (Cn) is the heaviest of these metals. First created in 1996, it is a man-made element that does not occur in nature.
Elements are created in the cores of stars by a process called stellar nucleosynthesis, in which the protons and neutrons of lighter elements are bonded together to form heavier ones. Iron (atomic number 26) is the heaviest element that can be created without requiring additional energy. Stars producing elements heavier than iron suffer a dramatic drop in energy output, leading to collapse and eventual supernova.
.7 -dMOST ABUNDANT METAL IN THE UNIVERSE
? Iron (Fe) accounts for approximately 0.11% of all matter in the universe. The sixth most common element overall, it makes up around 0.1% of the Sun and 0.006% of a human being. It also accounts for around 22% of meteorite material found on Earth – such as the famous WiIlamette Meteorite (left), a giant chunk of iron-nickel space debris weighing 14.15 tonnes (31,195 lb) that was discovered in the US state of Oregon.
More than half of the world’s output of lead is used to make car batteries
An average 70-kg (154-lb) human body comprises about 0.01% heavy metals (7 g, the weight of two dried peas)
A FIRST ALLOY
Alloys are mixtures of metals with other metals and occasionally non-metallic substances. The first alloy created by humans was bronze, which is copper mixed with approximately 10% tin. The Bronze Age, which began in the ancient Near East around the 4th millennium bce, marked the period when this alloy became the material of choice for weapons and tools. The era saw the development of mining and smelting techniques, as well as the formation of trade networks between early civilizations.
ASOFTEST METALLIC ELEMENT
With a Mohs value of just 0.2, caesium (Cs) is soft enough to be cut with a butter knife. It melts at just 28°C (82°F) and explodes violently when dropped in water. Caesium was discovered in 1860 by the German scientists Robert Bunsen and Gustav Kirchhoff, who isolated it from a sample of mineral water using the recently developed technique of flame spectroscopy. Silvery-gold in colour, caesium’s most notable use is in super-accurate atomic clocks.
A LIGHTEST METAL THAT IS LIQUID NEAR ROOM TEMPERATURE
Discovered in 1875, the unusual metal gallium (Ga) possesses an atomic number of 31 and melts at just 29.76°C (85.56°F). Unlike liquid mercury, which is highly toxic, gallium is safe to handle and will melt in your hand. These properties have made it a key ingredient of a popular practical joke among some chemists, who serve tea with a gallium spoon that rapidly disappears upon stirring.
A DENSEST METAL
Discovered in 1803 by Smithson Tennant and William Hyde Wollaston (both U K), osmium (Os) has a density of
As established by the International Tungsten Industrial Association (ITIA), Tungsten (W) has a boiling point of 5,700“C (10,292“F), with a 200“C (392“F) margin of error each side. This is equivalent to the surface temperature of the Sun. Tungsten also has the highest melting point of any metal, at 3,422°C (6,191“F), with a 15“C (59°F) margin of error.
Its extraordinary heat resistance makes tungsten a useful metal for industrial applications such as drill-bits and furnaces.
22.59 g/cm3, about twice that of lead. The toxic nature of osmium’s oxides mean that it is rarely used in its natural form. However, its hard-wearing qualities make it ideal for use in alloys for electrical contacts and fountain-pen nibs. The least dense metal at room temperature is lithium, at 0.5334 g/cm3.
The alkaline earth metals occupy group two of the periodic table. They all occur naturally and have a shiny, silvery-white appearance. The heaviest is radium (Ra), with an atomic number of 88. Discovered by Marie and Pierre Curie (both FRA) in 1898, it is the only radioactive member of the alkaline earth metals. Radium is used in industrial imaging and radioluminescent devices.
Chromium (Cr) boasts a value of 8.5 on the Mohs scale, which measures the hardness of minerals by their scratch resistance to other materials. Lustrous and steely grey, chromium has both a high melting point and corrosion 1 resistance. When added to iron in sufficient quantities,
‘ it forms the corrosion-proof alloy known as stainless steel. Chromium takes its name from the Greek word for “colour” – trace amounts of the element are what make
rubies red. They are also responsible for the brilliant red hue of the samples of crocoite mineral (shown left), which were A retrieved from a