Category Chemistry

Magnesium was not discovered until the 19th century. But much before that, humans had been using compounds of magnesium. Isolating magnesium is a tough task. This is because the compounds of magnesium are highly stable and cannot be broken down easily.

Careful studies of magnesium and its compounds began in the mid 1700’s. Some of the earliest studies on magnesium and its compounds were carried out by Joseph Black, a Scottish physician and chemist.

He conducted various experiments on compounds of magnesium and published his studies in an article. Black’s article became famous in the scientific circles and he is sometimes given credit for ‘discovering’ magnesium.

Though Black’s experiments were famous, it was Sir Humphry Davy who first isolated magnesium. Davy passed an electric current through melted magnesium oxide. The current caused the compound to break apart, forming the impure magnesium metal and oxygen gas. But this was a strenuous task, requiring a large battery with 200 pairs of metal discs to isolate the metal!

In 1798, a French chemist, Louis-Nicolas Vauquelin discovered a brittle, steel-gray metal. It was found as a component of coal, oil, certain rock minerals, volcanic dust, and soil. This metal was named beryllium.

Beryllium is used to make an alloy – beryllium copper- which has a wide variety of uses. Beryllium copper is used to make springs, electrical contacts, spot-welding electrodes, and non-sparking tools.

This alloy absorbs a lot of heat energy without becoming as hot as other metals. It is used in high-speed aircraft, missiles, spacecraft, and communication satellites for the same reason. It is also used to make windshield frames, brake discs, support beams, and other structural components of the space shuttle.

Though ordinary light cannot pass through beryllium, X-rays seep through it. So, it is used in the windows of X-Ray machines and radiation detectors. It is used to make computer parts and instruments where lightness, stiffness, and stability are required and even in nuclear reactors.

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The method of spectroscopy was instrumental in the discovery of some elements. Spectroscopy is the process of analyzing light produced when an element is heated. Each element produces a different light when heated.

The spectrum of an element consists of a series of coloured lines. In many cases, the amount of an element present in a sample is too small. But, the element is much easier to detect by spectroscopy.

Caesium was discovered using spectroscopy by two German scientists, Robert Bunsen and Gustav Kirchhoff. It happened in 1859. Bunsen and Kirchhoff discovered caesium while they were busy studying a sample of mineral water taken from a spring.

At first, they identified the spectral lines for sodium, potassium, lithium, calcium, and strontium; these elements were well-known at that time. After removing these elements from the sample, they could still see two blue lines in the spectrum.

This was due to the presence of caesium. It was Bunsen who suggested calling the element caesium; it is derived from the Latin word for ‘sky blue’.

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Francium is one of the most radioactive elements in nature. Apart from being one of the least stable elements, it is also the second rarest naturally occurring element on Earth.

Marguerite Perey discovered francium in 1939. She chose to name the metal after France, the nation of its discovery. Francium is formed when uranium and thorium ores decay. It is usually made from radium in nuclear reactors.

Numerous experiments and calculations have been carried out since francium was discovered to study its basic physical and chemical properties. The half-life of this element is around 22 minutes.

Due to its high reactivity, francium is not used commercially. However, from experiments conducted on rats, scientists have proved that francium is a promising aid in the early diagnosis of cancer. This is because francium accumulates in cancerous tissues.

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Like sodium, potassium is another metal famous for its reactivity; it is so active that it never occurs freely in nature, but only as compounds. This was why our ancestors did not know about the existence of this metal. Potassium was not known to the world until the 19th century.

The term potassium comes from potash. Early humans were familiar with potash, a compound of potassium that was formed when wood burns. Wood ash was washed with water to dissolve the potash. It was then recovered by evaporating the water. By the late I700’s, chemists were reasonably sure that potash contained elements they had never seen. They tried to think of ways to break potash down into its elements. However, it was the English chemist Sir Humphry Davy who finally found a way to make potassium from potash.

In 1807, Humphry Davy prepared potassium in its pure form for the first time in the world. He was using his newly invented method of isolating elements, known as electrolysis. In electrolysis, electric current is passed through a molten or melted compound which breaks the compound into its elements.

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The reactivity of rubidium might surprise you. In fact, rubidium is one of the most reactive of all the metals in the world. It catches fire when exposed to oxygen in the air, and burns up with a bright pinkish purple flame to become a yellow powder called rubidium superoxide.

If you try to put out the fire with water, it will only make matters worse. Want to know why? Rubidium reacts vigorously with water as well! When exposed to water, it produces hydrogen gas, which catches fire and burns.

By now, you would have understood why it is difficult to store rubidium. Most of the containers are not suitable for preserving or storing rubidium. If you place it in an ordinary glass container, the rubidium will destroy the glass at high temperatures. The only solution is to store it in special glass tubes in which a vacuum is maintained, or in flasks of kerosene or paraffin oil.

The name ‘rubidium’ comes from the term ‘rubidus’, which was a word once used to refer to the deepest red.

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Sodium is notorious for its reactivity; it reacts quickly with air and water. Therefore, sodium is rarely used by itself though it is an important industrial metal. Let us now take a look at some of the uses of sodium.

Sodium is used for manufacturing many organic compounds and also to improve the structure of certain alloys. It is an indispensable element in the manufacture of soap, paper, textiles, glass and petroleum. We all consume sodium on a daily basis. There is a great variety in the compounds of sodium. Sodium silicates are used as fillers for salt, and in detergents. Sodium tetra borate is known as borax. Sodium hydroxide is used in the manufacture of paper, soap, rubber and rayon. It is also used for refining oil. Sodium fluoride is used in antibiotics, rat poison, and in ceramics. Sodium hydroxide gets grease out of the drains; it is also used to make liquid soap.

We consume sodium on a daily basis. The table salt that we use in our food is sodium chloride, a compound of sodium. Baking soda that we use to make baked goods is actually sodium bicarbonate, another compound of sodium.

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You might have heard of lithium batteries that are used in laptops and mobile phones. Lithium batteries replaced the lead-cadmium batteries as they are lightweight and not as toxic as their counterparts. The devices that use lithium batteries range from watches to spacecraft.

Lithium-6 is an isotope of lithium which is used as a fuel for nuclear reactors. Lithium is preferred as a nuclear fuel, because it is cheaper and more available. In addition to being a nuclear fuel, it is also used in rockets and spaceships. If lithium is added to water it produces highly flammable hydrogen.

Ceramics, enamels, glass, lubricants, rubber products and certain dyes also use lithium. It is used in some medicines as well. Lithium is used as an air purifier in submarines, aircraft and even air conditioners.

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Let us now look at the varied uses of mercury. Mercury is used as an electrode in the production of chlorine and sodium hydroxide. It is also used in certain electric batteries.

It is used in barometers and manometers. It is also used extensively in thermometers. Mercury is important as a liquid contact material for electric switches. It was also used in mercury-vapour lamps that were used for street lighting.

Mercury forms a special type of alloy with some metals like silver, and tin. These alloys are used in dentistry for filling teeth. Several compounds of mercury are used as disinfectants.

They are also used to make substances including insecticides and rat poison. Mercuric oxide is used in skin ointments, though of course people handle it with a great deal of care now, because of the danger of mercury poisoning.

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Mercury is not a common metal. It is rarely found on Earth’s crust. In fact, it forms only 0.00005 per cent of the crust. However, there are more than 20 minerals that contain mercury. It is found in cinnabar, cordierite, livingstonite and some other minerals, with cinnabar being the most common ore.

Mercury ores usually occur at hot springs or other volcanic regions. Globally, mercury is most commonly produced in Spain; the Almaden mine there is known for its high quality mercury. It is also obtained from the United States and Italy.

Mercury is named after the planet Mercury, which in turn, is named after the Roman God Mercurius, the God of trade, profit and commerce. Mercury is sometimes called quicksilver because of its silver colour. In fact, its chemical symbol ‘Hg’ comes from the Greek word ‘hydrargyrum’ which means ‘water silver’.