write a short note 1) noble metal 2) purity of gold
Answers
Answer:
In chemistry, noble metals are metallic elements that show outstanding resistance to chemical attack even at high temperatures.[8] They are well known for their catalytic properties and associated capacity to facilitate or control the rates of chemical reactions.[8] The short list of chemically noble metals (those elements upon which almost all chemists agree)[citation needed] comprises ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), platinum (Pt), and gold (Au).[9] In periodic table terms the noble metals correspond to the noble gases.[10]
Explanation:
Gold is a chemical element with the symbol Au (from Latin: aurum) and atomic number 79, making it one of the higher atomic number elements that occur naturally. In a pure form, it is a bright, slightly reddish yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal and a group 11 element. It is one of the least reactive chemical elements and is solid under standard conditions. Gold often occurs in free elemental (native) form, as nuggets or grains, in rocks, in veins, and in alluvial deposits. It occurs in a solid solution series with the native element silver (as electrum) and also naturally alloyed with copper and palladium. Less commonly, it occurs in minerals as gold compounds, often with tellurium (gold tellurides).
Answer:
Noble metal
According to this definition, gold, silver, and copper are noble metals. Another definition of a noble metal is one which resists oxidation and corrosion. This excludes copper, but adds in other platinum group metals, such as rhodium, palladium, ruthenium, osmium, and iridium...
Purity of gold
'Caratage' is the measurement of purity of gold alloyed with other metals. 24 carat is pure gold with no other metals. Lower caratages contain less gold; 18 carat gold contains 75 per cent gold and 25 per cent other metals, often copper or silver.