Lutetium

Lutetium is atom number 71 — every Lutetium atom has exactly 71 protons in its center, and that number is what makes it Lutetium and nothing else. Its symbol is Lu. At room temperature it is a solid.

Lutetium is a chemical element with symbol Lu and atomic number 71. It is a silvery white metal, which resists corrosion in dry, but not in moist air. It is considered the first element of the 6th-period transition metals and the last element in the lanthanide series, and is traditionally counted among the rare earths.

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

Lutetium sits in period 6, group 3 of the d-block. Its 71 electrons fill shells of 2, 8, 18, 32, 9, 2 — written as [Xe] 4f14 5d1 6s2. Its electronegativity is 1.27 on the Pauling scale, and pulling the first electron off takes 523.5 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 4f14 5d1
Ionization energies (kJ/mol): 523.5, 1340, 2022.3, 4370, 6445
Electron affinity: 33.4 kJ/mol · Electronegativity (Pauling): 1.27
Density: 9.841 g/cm³ · melts 1925 K · boils 3675 K

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