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38.9 x 38.9 cm ⏐ 15.3 x 15.3 in (300dpi)
SCIENCE PHOTO LIBRARY SCIENCE PHOTO LIBRARY
Praseodymium (Pr). Diagram of the nuclear composition and electron configuration of an atom of praseodymium-141 (atomic number: 59), the most common isotope of this element. The nucleus consists of 59 protons (red) and 82 neutrons (blue). 59 electrons (green) bind to the nucleus, successively occupying available electron shells (rings). Praseodymium is a lanthanide in period 6, and the f-block of the periodic table. It melts at 935 degrees Celsius. The trend across the lanthanides arises from the failure of electrons filling an inner f-subshell (here, within the 4th ring) to shield outer electrons from increasing nuclear charge.
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