Wikipedia: Copper (Popularity: )

Properties of the element, including its history, applications, and charateristics.

Visual Elements: Copper (Popularity: )

Image, general and physical information, source, uses, key isotopes, and ionisation energies.

Lenntech: Copper (Popularity: )

Physical data, chemical properties, health and environmental effects.

WebElements: Copper (Popularity: )

Extensive information on history, uses, occurrence, compounds, and properties of the element.

ChemicalElements.com: Copper (Popularity: )

Basic information, atomic structure, and table of isotopes.

EnvironmentalChemistry.com: Copper (Popularity: )

Atomic structure, chemical and physical properties, and table of nuclides.

USGS Minerals Information: Copper (Popularity: )

Statistics and information on the worldwide supply, demand, and flow of the element (PDF format).

Copper (Popularity: )

Properties and applications along with photographs and chemical formulas of occurrences.

It's Elemental: Copper (Popularity: )

Basic physical and historical information.

Radiochemistry of Copper (Popularity: )

Full text of the monograph by F. F. Dyer (Oak Ridge National Laboratory, Oak Ridge, ...