Chemical element native solid elements occur in alloys, such as that of iron and nickel. The history of the discovery and use of the elements began with primitive human societies that found native elements like carbon, sulfur, copper and gold. Later civilizations extracted elemental copper, tin, lead and iron from their ores by smelting, using charcoal. Alchemists and chemists subsequently identified many more; all of the naturally occurring elements were known by 1950. The properties of the chemical elements are summarized in the periodic table, which organizes the elements by increasing atomic number into rows ("periods") in which the columns ("groups") share
Element collecting auction sites such as eBay. Some commercial retailers now cater to the element collecting community, even selling large quantities in sets, since purchasing elements from large chemical companies like Sigma-Aldrich is frequently prohibited or uneconomical for individuals. There are a number of specialist element providers which retail to the public over the web, sell individual element samples in addition to full and partial element sets. Many also sell elements through auction sites, such as eBay. Established specialist providers include Nova Elements, RGB Elements, Smart Elements, Metallium, Collect the Periodic Table, Luciteria and Onyxmet. Element collecting presents many challenges: some elements,