61 2 · 8 · 18 · 23 · 8 · 2

Promethium, Pm, element 61

Lanthanide· Period 6· f-block

Configuration [Xe]4f⁵6s²

Atomic weight: 144.913Da
Phase: solid
Density: 7.26g/cm³
Melting point: 1,315.15K 1,042 °C
Boiling point: 3,273K 3,000 °C
Electronegativity: 1.13

Soft silvery metallic element, belongs to the lanthanoids. Pm-147, the only natural isotope, is radioactive and has a half-life of 252 years. Eighteen radioisotopes have been produced, but all have very short half-lives. Found only in nuclear decay waste. Pm-147 is of interest as a beta-decay source, however Pm-146 and Pm-148 have to be removed from it first, as they generate gamma radiation. Discovered by J.A. Marinsky, L.E. Glendenin and C.D. Coryell in 1947. 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 promethium

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.: 144.9128Da; Source: mendeleev
Electron configuration: [Xe]4f⁵6s²; 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.: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d¹⁰4f⁵5s²5p⁶6s²; Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.: 2 · 8 · 18 · 23 · 8 · 2; Source: Worked outfrom electron configuration

Screening of each subshell

Clementi's screening constants: how much of the nucleus's charge the other electrons hide from an electron in each subshell. What is left is the effective nuclear charge it feels.

Subshell	Screening σ	Effective charge Z − σ
1s	1.2042	59.7958
2s	16.0296	44.9704
2p	4.2562	56.7438
3s	19.8154	41.1846
3p	19.4461	41.5539
3d	13.9018	47.0982
4s	29.3604	31.6396
4p	30.3768	30.6232
4d	33.26	27.74
4f	37.866	23.134
5s	42.1645	18.8355
5p	44.586	16.414
6s	51.6046	9.3954