Gold (atomic symbol Au) has an atomic number of 79. It is a dense, shiny and soft metal and the most ductile (capable of being drawn out in a thin wire) metal known. Gold takes the form of nuggets, grains found in rocks, flakes that wash down stream beds and veins in the earth. A nugget of pure gold weighing 120 kilograms was found in Australia in 1869. Gold has a considerable specific weight, high-temperature melting and boiling points and relatively low hardness. Along with silver and copper, it is one of the best conductors of electricity and heat. All soluble compounds of gold are toxic.
Silver (Ag) occurs in nature in elemental form and in silver compounds. Silver is the best conductor of heat and electricity of all elements. It is soft, expansive and easy to mold and contains several minerals, including argentite (Ag2S), as byproducts. Due to specific physical and chemical properties of its alloys and its compounds, silver has numerous applications in industry and electronics. The atomic number of silver is 47, the melting point is 961.93 degrees Celsius and the boiling point 2,212.0 degrees Celsius.
Platinum (Pt) is grouped in the transition metals on the periodic table of elements. Platinum has 36 isotopes whose atomic masses are between 172 and 201. It occurs in the Earth's crust in the form of platinum ores and as a companion to nickel and copper ore. In America it was known before Christopher Columbus. The Spaniards brought platinum in Europe in 1750, and thought it was just another kind of silver. That is why the name comes from the Spanish word platina, which means silver. The most important compounds of platinum are hexachloroplatinic acid and complex organometallic compounds. Platinum is non-toxic and does not cause cancer. Some of its compounds are used in chemotherapy to fight certain cancers. In its pure form, it looks like a silvery white metal. It is malleable and can easily be modeled into wires.
Palladium (Pd) is also a transition metal with 25 isotopes whose atomic masses are between 96 and 116. Palladium was discovered in 1803 by William Hyde Wollaston and it is mainly found as a companion of copper and zinc. The name comes from the planetoid Pallas. It is a shiny, silvery metal, malleable and ductile with an atomic number of 46 and a melting point of 1,552 degrees Celsius.