Francium

Francium is atom number 87 — every Francium atom has exactly 87 protons in its center, and that number is what makes it Francium and nothing else. Its symbol is Fr. At room temperature it is a solid.

Francium is a chemical element with symbol Fr and atomic number 87. It used to be known as eka-caesium and actinium K. It is the second-least electronegative element, behind only caesium. Francium is a highly radioactive metal that decays into astatine, radium, and radon.

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

Francium sits in period 7, group 1 of the s-block. Its 87 electrons fill shells of 2, 8, 18, 32, 18, 8, 1 — written as [Rn] 7s1. Its electronegativity is 0.79 on the Pauling scale, and pulling the first electron off takes 380 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 6s2 4f14 5d10 6p6 7s1
Ionization energies (kJ/mol): 380
Electron affinity: 46.89 kJ/mol · Electronegativity (Pauling): 0.79
Density: 1.87 g/cm³ · melts 300 K · boils 950 K

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