XI Note-making -
Class-XI Q.Read the following extract carefully and make the notes with the help of the clues given below. Note-making -(03 Marks) Naturally occurring platinum and platinum rich alloys have been known for a long time. The Spaniards named the metal 'platina' or little silver, when they first encountered it in Columbia. The platinum group metals are rhodium, ruthenium, palladium,osmium, iridium and platinum. Of these, platinum is the most important. These metals are very similar in many ways and are extremely rare. On average, there is only a gramme of ruthenium in each tonne of rock and barely a gramme of rhodium in over a 1000 tonnes of rock! Platinum's wear and tarnish resistance characteristics are well suited for making fine jewellery. Other distinctive properties include- resistance to chemical attack, excellent high temperature characteristic and stable electric properties. These metals are uniquely durable and can be used extremely efficiently- meanin...