Polonium

Polonium is atom number 84 — every Polonium atom has exactly 84 protons in its center, and that number is what makes it Polonium and nothing else. Its symbol is Po. At room temperature it is a solid.

Polonium is a chemical element with symbol Po and atomic number 84, discovered in 1898 by Marie Curie and Pierre Curie. A rare and highly radioactive element with no stable isotopes, polonium is chemically similar to bismuth and tellurium, and it occurs in uranium ores. Applications of polonium are few.

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

Polonium sits in period 6, group 16 of the p-block. Its 84 electrons fill shells of 2, 8, 18, 32, 18, 6 — written as [Xe] 4f14 5d10 6s2 6p4. Its electronegativity is 2 on the Pauling scale, and pulling the first electron off takes 812.1 kJ/mol. The outermost shell holds 6 electrons — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p4
Ionization energies (kJ/mol): 812.1
Electron affinity: 136 kJ/mol · Electronegativity (Pauling): 2
Density: 9.196 g/cm³ · melts 527 K · boils 1235 K

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