Thulium

Thulium is atom number 69 — every Thulium atom has exactly 69 protons in its center, and that number is what makes it Thulium and nothing else. Its symbol is Tm. At room temperature it is a solid.

Thulium is a chemical element with symbol Tm and atomic number 69. It is the thirteenth and antepenultimate (third-last) element in the lanthanide series. Like the other lanthanides, the most common oxidation state is +3, seen in its oxide, halides and other compounds.

Summary from the source dataset, derived from Wikipedia (CC BY-SA 3.0) · original article

Thulium sits in period 6, group 3 of the f-block. Its 69 electrons fill shells of 2, 8, 18, 31, 8, 2 — written as [Xe] 4f13 6s2. Its electronegativity is 1.25 on the Pauling scale, and pulling the first electron off takes 596.7 kJ/mol. The outermost shell holds 2 electrons — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f13
Ionization energies (kJ/mol): 596.7, 1160, 2285, 4120
Electron affinity: 99 kJ/mol · Electronegativity (Pauling): 1.25
Density: 9.32 g/cm³ · melts 1818 K · boils 2223 K

Values exactly as published — see where the data comes from.