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Chromium (Cr). Diagram of the nuclear composition and electron configuration of an atom of chromium-52 (atomic number: 24), this element's most common isotope. The nucleus consists of 24 protons (red) and 28 neutrons (blue). Chromium is a transition metal in group 6, period 4, and the d-block of the periodic table. It has a melting point of 1907 degrees Celsius. The trends across the transition metals are due to electrons filling an inner d-subshell (here, within the 3rd ring), shielding the outer electrons from the increasing nuclear charge.
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