Holmium

Holmium is atom number 67 — every Holmium atom has exactly 67 protons in its center, and that number is what makes it Holmium and nothing else. Its symbol is Ho. At room temperature it is a solid.

Holmium is a chemical element with symbol Ho and atomic number 67. Part of the lanthanide series, holmium is a rare earth element. Holmium was discovered by Swedish chemist Per Theodor Cleve.

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

Holmium sits in period 6, group 3 of the f-block. Its 67 electrons fill shells of 2, 8, 18, 29, 8, 2 — written as [Xe] 4f11 6s2. Its electronegativity is 1.23 on the Pauling scale, and pulling the first electron off takes 581 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 4f11
Ionization energies (kJ/mol): 581, 1140, 2204, 4100
Electron affinity: 32.61 kJ/mol · Electronegativity (Pauling): 1.23
Density: 8.79 g/cm³ · melts 1734 K · boils 2873 K

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