Finding and Using Metals The relationship between the reactivity of a metal and when it was discovered. By Sana Amin , 8B

History of Metals Metals were known to human since the ancient times. However they didn’t know how to make use of metals in the best way. For them it was just a tool to make arrows and spear tips. Later did they find the more helpful use of metals such as building material for various objects. The knowledge of its refining and processing to yield a useful product took thousands of years. We will analyze information to see if there is a relationship exists between the reactivity of a metal and when it was discovered.

First Metals The first metals that were used by humans were gold and copper. The softness and malleability of gold meant it was mainly used for ornamental purposes. Copper, the more harder metal was used for spearheads, knives, pins and other useful items Here is the timeline of the discovery of the first metals. (1) Gold 6000BC (2) Copper 4200BC (3) Silver 4000BC (4) Lead 3500BC (5) Tin 1750BC (6) Iron, smelted, 1500BC (7) Mercury, (ca) 750BC

Gold Gold the least reactive of metals was discovered the earliest in 6000BC . Gold was considered important even then . Many ancient central American tribes believed in the importance of gold for religious beliefs . The Inca’s believed it was the sweat of their sun god that’s why the Incas honored him with magnificent golden artworks. The presence of gold eventually led to their destruction as the Spanish conquistadors (conquerors) plundered them under their leaders, Pizarro and Cortes. This shows us the social affects some metals have had on civilizations. Even in recent times South Africa was colonized by Europeans because of its vast gold reserves.

Medieval Metals As the means of technology improved such as the discovery of fire and use of mining tools, more metals were discovered. People found different uses for the softer metals and replaced making of tools and weapons with the newer harder metals. For example copper was used to make the blades of swords and spear tips, after tin was discovered people started using copper in pottery as tin was more efficient in making weapons than copper was.

Newer Methods discover newer metals There are various methods of extractions. Smelting is when an ore is heated to high temperatures to separate a metal from its impurities. This method is commonly used to extract Iron. Another common method is Electrolysis. Which utilizes passing electricity through a solution to separate metals. Likewise displacement of metals technology can be used to remove a metal from its compound. For example in class we learnt that we can separate copper from Copper Sulphate solution by mixing it with magnesium. Listed below are some metals that were discovered later on. Zinc – was discovered in Germany by the chemist Andreas Marggraf in 1746. It was isolated two years later by Anton von Swab. It was isolated by heating calamine and carbon. Aluminum - was discovered in Denmark by Hans Christian Oersted in 1825. It is obtained by performing the electrolysis method. Sodium – was first isolated by Sir Humphry Davy in 1807 by passing an electric current through molten sodium hydroxide. Magnesium- was discovered by Joseph Black, in England, in 1755. It was first isolated by Sir Humphry Davy, an English chemist, through the electrolysis of a mixture of magnesium oxide and mercuric oxide in 1808. Today, magnesium is most often obtained from seawater.

Relative reactivity of metals Now that we have some information about discovery of metals let us analyze the reactivity series. The Reactivity Series is a list of metallic elements, where the more reactive metals are listed at the top and less reactive ones at the bottom. Some metals react more easily than others. The reactive metals react quickly with acid, oxygen, and water. The alkali metals are a very reactive group of metals.

Size of an atom vs. reactivity The further down a group an atom is, the larger the atom is, and the more reactive the element is. The reactivity of metals increases as you go down the group because the outer electrons are further from the nucleus as the atom is larger. This means that it is harder for the nucleus to keep a pull on the outer electron making the metal reactive. For example the highly reactive metal Cesium which is located in group 1 of the periodic table therefore an alkali metal has the atomic number of 55 which means it has 55 electrons.

Reactivity series of metals An element is more reactive if it is further to the left of the periodic table or further down. The exceptions to this are the transition metals as they have special D electrons.

Reactivity vs. discovery Metal Date of Discovery ( approximately ) Reactivity ( relative position) Gold 6000BC 2 (Least reactive) Iron 1200BC 8 Zinc 1746 9 Aluminum 1825 11 Magnesium 1755 12 Potassium 1807 15 (Highly reactive)

Relationship As you can see with the exception of aluminum there is a relationship between the reactivity of a metal and the date it was discovered. The data shows that least reactive metals were discovered earlier because they exist in nature in almost pure form. The least reactive metals such as gold and copper exist naturally and can be found in form of nuggets. The more reactive metals exist in compound form and need advanced technology to separate them. Even today there are many metals which can only be extracted to its pure form in a laboratory only.

Conclusion In conclusion I would like to say that there is a direct relationship between when a metal was discovered and it reactivity. Science has played a vital role in discovery of newer metals which had a very big impact on the lives we live today. For example without the discovery of electrolysis scientist may have never discovered aluminum and with out aluminum we might have never had the airplanes we have today. Airplanes allow us to travel long distances much quickly than the old air travel like that of using blimp.  

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