Zirconium

Zirconium is atom number 40 — every Zirconium atom has exactly 40 protons in its center, and that number is what makes it Zirconium and nothing else. Its symbol is Zr. At room temperature it is a solid.

Zirconium is a chemical element with symbol Zr and atomic number 40. The name of zirconium is taken from the name of the mineral zircon, the most important source of zirconium. The word zircon comes from the Persian word zargun زرگون, meaning "gold-colored".

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

Zirconium sits in period 5, group 4 of the d-block. Its 40 electrons fill shells of 2, 8, 18, 10, 2 — written as [Kr] 4d2 5s2. Its electronegativity is 1.33 on the Pauling scale, and pulling the first electron off takes 640.1 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 4d2
Ionization energies (kJ/mol): 640.1, 1270, 2218, 3313, 7752, 9500
Electron affinity: 41.806 kJ/mol · Electronegativity (Pauling): 1.33
Density: 6.52 g/cm³ · melts 2128 K · boils 4650 K

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