Platinum

Platinum is atom number 78 — every Platinum atom has exactly 78 protons in its center, and that number is what makes it Platinum and nothing else. Its symbol is Pt. At room temperature it is a solid.

Platinum is a chemical element with symbol Pt and atomic number 78. It is a dense, malleable, ductile, highly unreactive, precious, gray-white transition metal. Its name is derived from the Spanish term platina, which is literally translated into "little silver".

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

Platinum sits in period 6, group 10 of the d-block. Its 78 electrons fill shells of 2, 8, 18, 32, 17, 1 — written as [Xe] 4f14 5d9 6s1. Its electronegativity is 2.28 on the Pauling scale, and pulling the first electron off takes 870 kJ/mol. The outermost shell holds 1 electron — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s1 4f14 5d9
Ionization energies (kJ/mol): 870, 1791
Electron affinity: 205.041 kJ/mol · Electronegativity (Pauling): 2.28
Density: 21.45 g/cm³ · melts 2041.4 K · boils 4098 K

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