Page 29 - Curriculum Visions Dynamic Book

The reactivity of silver
Metals can be arranged in a list called the reactivity series,
alloy: a mixture of a metal and various other elements.
with the most reactive at the top and the least reactive at noble metal: silver, gold, platinum, and
the bottom.
Silver is near the bottom of the reactivity series because
mercury. These are the least reactive metals.
it is only very slightly reactive. This low reactivity means that precious metal: silver, gold,
silver compounds are rarely produced in nature, and silver has very limited uses in chemistry. It will not react with the air to form oxides, although it does react with polluted air to form silver sulphide. This is, in fact, the chemical composition of the tarnishing seen on silver jewellery, cutlery, and decorative ware, as described below.
platinum, iridium, and palladium.
Each is prized for its rarity. This category is the equivalent of precious stones, or gemstones, for minerals.
reactivity: the tendency of a substance to react with other substances. The term is most widely used in comparing the reactivity of metals. Metals are arranged in a reactivity series.
 Silver metal reacts with hydrogen sulphide gas in the air to produce black silver sulphide.
REACTIVITY SERIES
Element
Reactivity
potassium sodium calcium magnesium aluminium manganese chromium zinc
iron cadmium tin
lead copper mercury silver gold platinum
most reactive
least reactive
Tarnish
Tarnish is the dark brown or black film that develops slowly
on silverware, especially in industrial cities. Silver does not react with oxygen, so tarnish is not an oxide coating. Rather,
it is a reaction of the silver with hydrogen sulphide in the air, especially the air near industrial cities. The result is a black film of silver sulphide as shown on the fork above and to the right.
Some silver tableware can tarnish (for example, the ends of forks) because some foods contain hydrogen sulphide. Hard boiled eggs are an example. The hydrogen sulphide effect can also be seen in the dark ring around the yolk.
EQUATION: Tarnishing of silver
Silver + hydrogen sulphide + oxygen ➪ silver sulphide + water 4Ag(s) + 2H2S(g) + O2(g) ➪ 2Ag2S(s) + 2H2O(l)
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