91 2 · 8 · 18 · 32 · 20 · 9 · 2

Protactinium, Pa, element 91

Actinide· Period 7· f-block

Configuration [Rn]5f26d17s2

Atomic weight
231.036Da
Phase
solid
Density
15.4g/cm³
Melting point
1,845.15K 1,572 °C
Boiling point
4,300K 4,027 °C
Electronegativity
1.5

Radioactive metallic element, belongs to the actinoids. The most stable isotope, Pa-231 has a half-life of 2.43*10^4 years. At least 10 other radioactive isotopes are known. No practical applications are known. Discovered in 1917 by Lise Meitner and Otto Hahn. Description from mendeleev.

Back to the table
The outermost shell: the valence electronsThe inner shellsThe nucleus One bead for each electron, on the ring of its shell, counted from the nucleus out. The rings turn at their own pace; the model is Bohr's picture of the atom, which places electrons in shells but not on true orbits.

Atomic properties

5 of 5 fields have a value for protactinium

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.
231.0359Da
Source: mendeleev
Electron configuration
[Rn]5f26d17s2
Source: mendeleev
Uncertainty of the atomic weight
2×10−5Da
Source: mendeleev
Electron configuration in full The electron configuration with the noble-gas core written out.
1s22s22p63s23p63d104s24p64d104f145s25p65d105f26s26p66d17s2
Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.
2 · 8 · 18 · 32 · 20 · 9 · 2
Source: Worked outfrom electron configuration