BBC Chemistry- A Volatile History

Part 1: Discovering the Elements

Just in the last two hundred years we have had the term of element. The Ancient Greeks didn´t know this fact, so they divided the elements into four basic elements: earth, water, fire and air. It was first a Swiss alchemist Paracelsus that tried to challenge the Greek idea of four elements. He was as well a surgeon; he used his alchemical knowledge with the surgery. It was very controversial. According to him there were three elements: sulphur, salt and mercury.

Later on Brand was searching for a way of extracting gold from the human body; he believed that by using urine it might contain life force. He discovered a substance which he named icy noctiluca, phosphorus as is known now. Nowadays phosphorus is found in loads of products of our daily life like toothpaste. A decade later Boyle wrote a book which was the turning point of alchemist to chemistry. This book was kept secret.

Johann Becker a German scientist said that fire was caused by phlogiston. It was supposed that this substance reduced the pure form of fire. It was accepted as a scientific truth.

In 1700 there were three airs: common air, Cavendish’s air and fixed air. Fixed air was very interesting for a minister whose hobby was the investigation of air. The minister discovered dephlogisticated air, apparently it contained within combustible bodies and released during combustion. Lavoisier a French scientist had the best equipped laboratory in Europe. Thanks to this he discovered a brand new element named oxygen. He created a classification for the chemicals being discovered. Inflammable air became hydrogen. A professor in London Humphry Davy investigated salts of potash. He heated the potash until it was liquid and he introduced two electrodes. The left substance was a never before seen element potassium. Davy added six new elements to Lavoisier list; he confirmed also chloride and iodine. Since then there was a new since:Chemistry.

Part 2: The Order of the Elements

The law of Octaves said that the elements were like eight musical tones. It was proposed by Newlands; however it was considered ridiculous at the time.

John Dalton discovered that the elements that the elements were unified in the same proportion by atoms. His theory was proved a century over. Different atoms of different elements have different weights. Berzelius a Swedish scientist discovered thanks to be a glass blower, a new element called silicon. The second most abundant element on Earth. He isolated four determine elements. He found the relative weights of 24 elements. The first periodic table was formulated by Dmitri Mendeleev; it was a great scientific achievement. The criteria for the table were to organise the table into weight and their reaction in water. However the table was incomplete of unknown elements. There were gaps because it wasn´t perfectly accurate and Mendeleev already knew that new elements would be discover. Even he predicted that calcium was going to appear in the table before someone else knew the existence of this element. Rubidium was discovered along a partner of Mendeleev, they discovered it by a spectroscope. During an eclipse in India a French astronomer saw the spectrum around the

moon during the eclipse, this spectral line was thought to be the only existed element in the sun, it was called helium. William Ramsay noticed that there was a missing column in the table; he found out the Noble Gases, argon, krypton, neon and xenon formed that new group.

Part 3: The Power of the Elements

Heinrich Diesbach was trying to create a red pigment. He heated potash, however he didn´t know that the potash was contaminated with blood. The proteins in the blood were combined with the iron. By adding other substances he obtained a brilliant colour called Prussian Blue.

A German chemist Justun von Liebig was obsessed with the understanding of the elements since he was a child. He was especially interested in explosive silver fulminate. He began a fight with Friedrich Wohler, according to Liebig he was a hopeless for saying that silver cyanate was made of equal parts of silver, carbon, nitrogen and oxygen. Afterwards both discovered isomerism: same number of atoms of the same elements combining in different ways to make different compounds.

Smithson Tennant decided to burn a diamond. With a magnified glass he produced gas in the diamond, and then he was able to determine that the gas was carbon dioxide. He discovered that diamonds were made of carbon. However scientists were unable to explain how carbon, a very soft substance, was the main element of the hardest substance.

Archibald Scott Couper came up with the idea of links in the atoms, he called them bonds. Couper realised that carbon could have four bonds. Therefore there are different strengths to other carbon atoms in a compound.

After the invention of Bakelite Wallace Carothers drew off a fibre from the interface of two liquids. He discovered nylon. However he killed himself.

Marie Curie discovered that pitchblende was four times more radioactive than uranium. Curie discovered two new elements polonium and radium.

David García Castro TY2