Tantalum is a hard, blue-gray, highly corrosion-resistant transition metal used in capacitors, high-temperature alloys, and chemical equipment; it forms a stable Ta2O5 oxide layer.
The electron configuration of tantalum is [Xe] 4f14 5d3 6s2. This arrangement gives tantalum its transition metal properties, with the 5d and 6s electrons participating in metallic bonding and chemical reactions.
Tantalum forms a dense and stable oxide layer, Tantalum(V) oxide (Ta2O5), when exposed to air. This oxide film adheres strongly to the metal surface and prevents further oxidation or attack by acids, making tantalum almost immune to chemical corrosion, even in aggressive environments like aqua regia.
\(\mathrm{4\,Ta(s) + 5\,O_2(g) \rightarrow 2\,Ta_2O_5(s)}\)
Tantalum has many important applications:
Tantalum primarily exhibits the +5 oxidation state (Ta5+) in most of its compounds, such as Ta2O5 and TaCl5. Lower oxidation states like +4, +3, and +2 can exist in some halides and complex compounds but are less stable.
Tantalum capacitors are valued because of their high capacitance-to-volume ratio and excellent reliability. The dielectric layer in these capacitors is made from tantalum oxide (Ta2O5), which has a very high dielectric constant, allowing for compact and durable electronic components.
Tantalum is highly resistant to most acids, including hydrochloric and nitric acid, due to the formation of its oxide film. However, it can be attacked by hydrofluoric acid (HF) and hot concentrated sulfuric acid, which dissolve the protective oxide layer.
Tantalum is a hard, dense, and ductile metal with a melting point of approximately 3017 °C and a boiling point of about 5458 °C. It has excellent electrical conductivity and a blue-gray luster.
Tantalum is found primarily in the minerals tantalite [(Fe,Mn)Ta2O6] and columbite [(Fe,Mn)(Nb,Ta)2O6], often together with niobium. Major deposits occur in countries such as Australia, the Democratic Republic of the Congo, and Brazil.
Tantalum is considered biocompatible and non-toxic, which is why it is used in medical implants and surgical tools. However, tantalum dust or fumes may cause irritation and should be handled with standard safety precautions.
A common reaction is the formation of tantalum pentachloride when tantalum reacts with chlorine gas:
\(\mathrm{2\,Ta(s) + 5\,Cl_2(g) \rightarrow 2\,TaCl_5(s)}\)
TaCl5 is a volatile compound used as a precursor in chemical vapor deposition (CVD) of tantalum films.