Saturday, September 13, 2014

Gold and Platinum

Gold and platinum are considered to be metals used for jewellery making, and they are expensive. Both are less reactive elements and are ideal for jewelleries.
Gold
Gold is a transition metal with the chemical symbol Au. Au is from the Latin word ‘aurum’ which means ‘shining dawn’. Gold is in the group 11 of the periodic table, and its atomic number is 79. Its electron configuration is [Xe] 4f14 5d10 6s1. Gold is a shiny metal with a metallic yellow colour. Further, it is a malleable and ductile metal.
Gold is widely used to make jewellery and statues. It is considered as a very precious metal. One of the important properties of gold is its less reactivity. Gold doesn’t react with moisture and oxygen in the air. Therefore, no matter how long it is exposed to air, gold oxide layer won’t be forming; therefore, its colour doesn’t fade or change.
Since gold does not react with other chemicals easily, it occurs as a free element in the nature. Gold particles are found embedded in rocks. Johannesburg, South Africa has one of the largest gold deposits. Other than that, Russia, United States, Australia, and Peru are major gold producers in the world.
Gold creates alloy with other metals easily. Gold has +1 and +3 oxidation states commonly. Gold ions in a solution can be easily reduced to the 0 oxidation state, so gold can be precipitated out. 197Au is the only stable isotope of gold. Among the applications of gold, it has been in use for centuries. It was considered precious from the history and was being used as a currency. When making jewellery, pure gold (24k) is not used. Usually it is alloyed with some other metals and 22k, 18k, 9k etc. gold are used for jewellery making process.
Platinum
Platinum or Pt is a transition metal with the atomic number 78. In the periodic table, it is in the group with Nickel and Palladium. So has the electric configuration similar to Ni with outer orbitals having sd8arrangement. Platinum, most commonly, forms +2 and +4 oxidation states. It can also form +1 and +3 oxidation states.
Platinum is silvery white in colour and has a higher density. It has six isotopes. Among these, most abundant one is 195Pt.  Atomic mass of Platinum is about 195 gmol-1. Platinum doesn’t oxidize or react with HCl or nitric acid. It is highly resistant to corrosion. Pt also can withstand a very high temperature without melting. (Its melting point is 1768.3 °C) Also, it is paramagnetic.
Platinum is a very rare metal, which is used in jewellery making. Platinum jewellery is also known as white gold jewellery and is very expensive. Further it can be used as the electrode in electrochemical sensors, and cells.  Platinum is a good catalyst to use in chemical reactions. South Africa is the number one producer of platinum metal.
Gold vs Platinum
  • Platinum has the atomic number of 78, and atomic number of gold is 79.
  •  Platinum, most commonly, forms +2 and +4 oxidation states, but gold commonly forms +1 and +3 oxidation states.
  •  Gold has a metallic yellow colour whereas platinum has a shiny white colour.
  •  Platinum is used to make white gold jewelleries which are more expensive than gold jewelleries.


  •  When making jewellery, platinum can be used in more pure form compared to gold.

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