Problem 43 - Chemistry: The Central Science

Question

Which element or elements are alloyed with gold to make the following types of "colored gold" used in the jewelry industry? For each type, also indicate what type of alloy is formed: (a) white gold, (b) rose gold, (c) green gold.

Step-by-Step Solution

Answer

(a) White gold is made by alloying gold with palladium, nickel, or silver, forming a substitutional alloy. (b) Rose gold is made by adding copper to gold, also forming a substitutional alloy. (c) Green gold is created by mixing gold with silver, resulting in a substitutional alloy.

Step 1: (a) White Gold

White gold is formed by alloying gold with other elements that will lighten its color. These elements usually include metals like palladium, nickel, and silver. The type of alloy formed depends on the exact composition of the gold and other metals used. For this type of colored gold, the alloy is called a substitutional alloy because the atoms of the added metals are similar in size to the gold atoms and replace some of the gold atoms in the gold's crystal structure.

Step 2: (b) Rose Gold

Rose gold gets its distinct color from the addition of copper to gold. The increased copper content gives the alloy a reddish hue, and this color can vary in shade depending on the exact proportions of the gold and copper used. The type of alloy formed by gold and copper is again a substitutional alloy, due to the similar atomic size of the involved metals.

Step 3: (c) Green Gold

Green gold is created by alloying gold with silver. The ratio of gold to silver determines the shade of green in the resulting alloy. Often, a natural greenish hue occurs at 75% gold and 25% silver composition. Like the other colored golds, green gold is formed by a substitutional alloy because the added silver atoms have a similar size to those of the gold atoms and replace some of the gold atoms in the structure. In summary, gold is alloyed with different metals to create various "colored golds" for the jewelry industry: (a) White gold is formed by alloying gold with palladium, nickel, or silver; (b) Rose gold is formed by adding copper to gold; (c) Green gold is created by mixing gold with silver. In all of these cases, the type of alloy formed is a substitutional alloy due to the similar atomic sizes of the involved metals.