Answer is: zirconium (Zr).
Atomic number of zirconium (Zr) is 40, which means it has 40 protons and 40 electrons.
Electron configuration of zirconium atom:
₄₀Zr 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶4d²5s².
Zirconium has four valence electrons, it is in group 4 and period 5.
Zirconium is a lustrous, grey-white, strong transition metal.