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Ta

Tantalum

Tantalum (Ta) is a transition metal with atomic number 73 and an atomic mass of 180.95. Its electron configuration is [Xe] 4f14 5d3 6s2.

Tantalum key data

Symbol Ta
Atomic number 73
Atomic mass (standard atomic weight) 180.95
Molar mass 180.95 g/mol
Protons 73
Neutrons (most abundant isotope, tantalum-181) 108
Electrons (neutral atom) 73
Category Transition metal
Period 6
Group 5
Block d-block
Noble gas notation [Xe] 4f14 5d3 6s2
Full electron configuration 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d3 6s2
Electrons per shell 2, 8, 18, 32, 11, 2

Atomic mass: IUPAC CIAAW abridged standard atomic weights, 2024. Most abundant isotope: NIST Atomic Weights and Isotopic Compositions.

The values are facts and free to use; this page’s selection and presentation are © 2026 ScienceQuest.

Measured properties of tantalum

From PubChem, the US National Institutes of Health. Public domain. The first ionisation energy is the value for tantalum from the NIST Atomic Spectra Database, in place of PubChem’s 7.89 eV.

Melting point 3290 K (3016.9 °C), 5th of 103 by melting point
Boiling point 5731 K (5457.9 °C), 3rd of 93 by boiling point
Density 16.4 g/cm³, 10th of 96 by density
State at room temperature Solid
Electronegativity 1.5 (Pauling), joint 54th of 95 by electronegativity
Van der Waals radius 217 pm, joint 37th of 99 by atomic radius
First ionisation energy 7.5496 eV (728.43 kJ/mol), 43rd of 102 by first ionisation energy
Electron affinity 0.322 eV (31.1 kJ/mol), 49th of 57 by electron affinity
Common oxidation states +5
Discovered 1802

Each rank counts down from the highest value, among the elements PubChem’s table gives one for, and links to that property ranked across the whole table. All of them are collected under periodic trends.

Tantalum electron configuration

The full electron configuration of tantalum is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 4f14 5s2 5p6 5d3 6s2. With the noble-gas core collapsed it is [Xe] 4f14 5d3 6s2, and the outermost subshell is 6s2.

Bohr model of tantalum (Ta): a nucleus and six shells holding 2, 8, 18, 32, 11 and 2 electrons from the inside out.
Bohr model of tantalum (Ta). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.
Orbital box diagram of tantalum (Ta), [Xe] 4f14 5d3 6s2, with the xenon core drawn as one bar: one box per orbital, filled by Hund’s rule, showing three unpaired electrons, in 5d.
Orbital diagram of tantalum (Ta). Image © ScienceQuest, CC BY 4.0: free to reuse with credit to ScienceQuest and a link to this page, as the image licence explains.

Why group and block follow from this is set out in how the periodic table maps electron configuration, and the electron configuration of every element is listed on one page.

Mass of one tantalum atom

A molar mass is grams per mole, so dividing by the Avogadro constant gives the mass of a single atom, or for an element with more than one natural isotope the average mass of its atoms, and the reciprocal gives how many atoms sit in a gram.

Mass of one atom

  1. one atom = 180.95 / (6.02214076 × 10²³)
  2. = 3.0047 × 10⁻²² g

Atoms in one gram

  1. atoms per gram = 6.02214076 × 10²³ / 180.95
  2. = 3.3281 × 10²¹ atoms

Tantalum on the periodic table

Tantalum is in period 6, group 5, in the d-block.

The other elements of group 5 are vanadium, niobium and dubnium.

The rest of period 6

Work with tantalum