Cerium

Cerium is atom number 58 — every Cerium atom has exactly 58 protons in its center, and that number is what makes it Cerium and nothing else. Its symbol is Ce. At room temperature it is a solid.

Cerium is a chemical element with symbol Ce and atomic number 58. It is a soft, silvery, ductile metal which easily oxidizes in air. Cerium was named after the dwarf planet Ceres (itself named after the Roman goddess of agriculture).

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

Cerium sits in period 6, group 3 of the f-block. Its 58 electrons fill shells of 2, 8, 18, 19, 9, 2 — written as [Xe] 4f1 5d1 6s2. Its electronegativity is 1.12 on the Pauling scale, and pulling the first electron off takes 534.4 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 5d1 4f1
Ionization energies (kJ/mol): 534.4, 1050, 1949, 3547, 6325, 7490
Electron affinity: 55 kJ/mol · Electronegativity (Pauling): 1.12
Density: 6.77 g/cm³ · melts 1068 K · boils 3716 K

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