Coinage metal oxidation numbers

Like all the coinage metals, copper forms compounds with oxidation number + 1. However, in water, copper(I) salts disproportionate into metallic copper and copper(II) ions. The latter exist as pale blue [Cu(H20)6]2+ ions in water. 

Ans. (a) Pb4 + and Pb2+. (The maximum oxidation state of a group IV element and the state 2 less than the maximum.) (b) Tl3+ and Tl+. (The maximum oxidation state of a group III element and the state 2 less than the maximum.) (c) Sn4+ and Sn2+. (The maximum oxidation state of a group IV element and the state 2 less than the maximum.) (d) Cu+ and Cu2 +. (The maximum oxidation state for the coinage metals is greater than the group number.)... 

A number of trivial, yet useful and descriptive, designations continue to be used, e.g. alkali metals, alkaline earths (Be does not qualify, strictly speaking, as an alkaline earth because its amphoteric oxide is very weakly alkaline), the coinage metals (Cu, Ag, Au) and the noble (or inert, or rare) gases. 

The maximum oxidation number of any atom in any of its compounds is equal to its periodic group number, with a few exceptions. The coinage metals have the following maximum oxidation numbers Cu, +2 Ag, +2 and Au, +3. Some of the noble gases (group 0) have positive oxidation numbers. Some lanthanide and actinide element oxidation numbers exceed 3, their nominal group number. 

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