Element number 92 on the periodic table. Has an average atomic mass of 238.0 amu, 92 protons in its nucleus and 92 electrons orbiting around it. It has an electron ground state configuration of 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s2 5f3 6d1. It is the fourth element in the actinide series.
[Editor's note (Gz): Made factual correction 3/3/2002]