Tantalum is a metal element. It mainly exists in tantalite and coexists with niobium. Tantalum has moderate hardness and ductility. It can be drawn into filaments to make thin foils. Its thermal expansion coefficient is very small. Excellent chemical properties, high corrosion resistance, can be used to make evaporating vessels, etc., can also be used as electrodes, electrolysis, capacitors and rectifiers of electronic tubes.