Gadolinium

Gadolinium is atom number 64 — every Gadolinium atom has exactly 64 protons in its center, and that number is what makes it Gadolinium and nothing else. Its symbol is Gd. At room temperature it is a solid.

Gadolinium is a chemical element with symbol Gd and atomic number 64. It is a silvery-white, malleable and ductile rare-earth metal. It is found in nature only in combined (salt) form.

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

Gadolinium sits in period 6, group 3 of the f-block. Its 64 electrons fill shells of 2, 8, 18, 25, 9, 2 — written as [Xe] 4f7 5d1 6s2. Its electronegativity is 1.2 on the Pauling scale, and pulling the first electron off takes 593.4 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 4f7 5d1
Ionization energies (kJ/mol): 593.4, 1170, 1990, 4250
Electron affinity: 13.22 kJ/mol · Electronegativity (Pauling): 1.2
Density: 7.9 g/cm³ · melts 1585 K · boils 3273 K

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