69 2 · 8 · 18 · 31 · 8 · 2

Thulium, Tm, element 69

Lanthanide· Period 6· f-block

Configuration [Xe]4f136s2

Atomic weight
168.934Da
Phase
solid
Density
9.321g/cm³
Melting point
1,818.15K 1,545 °C
Boiling point
2,223.15K 1,950 °C
Electronegativity
1.25

Soft grey metallic element that belongs to the lanthanoids. One natural isotope exists, Tm-169, and seventeen artificial isotopes have been produced. No known uses for the element. Discovered in 1879 by Per Theodor Cleve. 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 thulium

Atomic weight The standard atomic weight. For an element with no stable isotope, the mass of its longest-lived isotope.
168.9342Da
Source: mendeleev
Electron configuration
[Xe]4f136s2
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.
1s22s22p63s23p63d104s24p64d104f135s25p66s2
Source: Worked outfrom electron configuration
Electrons in each shell Counted from the electron configuration, from the first shell outward.
2 · 8 · 18 · 31 · 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.

SubshellScreening σEffective charge Z − σ
1s1.343767.6563
2s18.052250.9478
2p4.358864.6412
3s21.081647.9184
3p20.523948.4761
3d13.625755.3743
4s31.862437.1376
4p33.01235.988
4d36.05632.944
4f40.36628.634
5s48.96320.037
5p51.27217.728
6s60.41588.5842