Trace of the U decay chain, separated by ion exchange from spent uranium fuel liquor. The world stock (~125 g) was pulled by the UKAEA in 1961.
Research Elements Pa · atomic number 91 Actinide · period 7 [Rn] 5f2 6d1 7s2 Shells: 2, 8, 18, 32, 20, 9, 2 Valence electrons: 2 in the outer shell (7s2), and 3 in 5f2 6d1 Green dots are the outer shell's s and p electrons. Softer green dots are the d electrons of transition metals, and the d and f electrons of lanthanides and actinides: they often take part in bonding, but not always. Grey dots are the core. Ground-state configuration from the NIST Atomic Spectra Database (A. Kramida, Yu. Ralchenko, J. Reader and the NIST ASD Team). Abundance is the mole fraction of the element found as that isotope on Earth; digits in parentheses are the uncertainty in the last digits. Masses and abundances from NIST, Atomic Weights and Isotopic Compositions (J. S. Coursey, D. J. Schwab, J. J. Tsai and R. A. Dragoset, National Institute of Standards and Technology).Protactinium
Electrons
How it's obtained
Natural isotopes
Isotope Relative atomic mass Abundance 231Pa 231.0358842(24) 1