Tantalum (Ta)
Tantalum (Ta) is a transition metal with atomic number 73 and a standard atomic weight of 180.95. At room temperature it is a solid that melts at 3,017 °C and boils at 5,455 °C.
Tantalum key facts
Tantalum at a glance
Identity
| Symbol | Ta |
|---|---|
| Atomic number (Z) | 73 |
| Atomic weight | 180.95 ± 0.01 (CIAAW 2024) |
| Category | Transition metal |
| Group | 5 |
| Period | 6 |
| Block | d-block |
| CAS number | 7440-25-7 |
Atomic properties
| Electron configuration | [Xe] 4f14 5d3 6s2 Full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d3 6s2 |
|---|---|
| Electrons per shell | 2, 8, 18, 32, 11, 2 |
| Oxidation states | +5 Less common: -3, -1, 0, +1, +2, +3, +4 |
| Electronegativity (Pauling) | 1.5 |
| First ionisation energy | 7.55 eV (728.4 kJ/mol) 2nd: 16.2 eV · 3rd: 23.1 eV |
| Electron affinity | 0.322 eV |
| Atomic radius (empirical) | 145 pm |
| Covalent radius | 146 pm |
| Van der Waals radius | 222 pm |
Physical properties
| State at 25 °C | Solid |
|---|---|
| Melting point | 3,017 °C · 5,462.6 °F · 3,290.15 K |
| Boiling point | 5,455 °C · 9,851 °F · 5,728.15 K |
| Density | 16.4 g/cm³ |
| Specific heat capacity | 0.14 J/(g·K) |
| Thermal conductivity | 57.5 W/(m·K) |
| Crystal structure | Body-centred cubic |
Isotopes & abundance
| Natural occurrence | Primordial |
|---|---|
| Radioactive | No |
| Natural isotopes (abundance) | 181Ta 99.988% |
| Stable isotopes | 1 |
| Known isotopes | 40 |
| Abundance in Earth's crust | 2 mg/kg |
| Abundance in seawater | 0.000002 mg/L |
Atomic weights: CIAAW Abridged Standard Atomic Weights 2024. Other properties: standard reference compilations, checked October 2026; predicted values are marked.
Tantalum electron configuration
Tantalum has 73 electrons. Written in short form, its ground-state configuration is [Xe] 4f14 5d3 6s2 — the electrons of the noble gas xenon, plus 4f14 5d3 6s2.Written out in full: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d3 6s2.
Discovery and name
1802 — Anders Gustaf Ekeberg · Sweden.
Tantalus of Greek myth — tantalum 'cannot drink' acids (it resists them).
Known for
Tantalum capacitors are in almost every phone and laptop. It is very corrosion-resistant and biocompatible, used in implants.
Isotopes of tantalum
Naturally occurring tantalum is a mix of 1 isotope. Each has 73 protons; they differ in the number of neutrons:
| Isotope | Protons | Neutrons | Natural abundance | Stability |
|---|---|---|---|---|
| 181Ta | 73 | 108 | 99.988% | stable |
40 isotopes of tantalum are known in our data set (half-lives as published in nuclear data tables).
Tantalum compared with group 5
The other elements in group 5, from top to bottom of the table: